Article

Adaptation to increased dietary salt intake in the rat. Role of endogenous nitric oxide

March 1993
The Journal of clinical investigation 91(2):642-50

March 1993
91(2):642-50

Source
PubMed

Authors:

Previous studies have suggested that nitric oxide (NO) plays a role in regulation of renal vascular tone and sodium handling. We questioned whether the effects of NO synthase inhibition on renal function are direct or due to increased renal perfusion pressure (RPP) and whether stimulation of endogenous NO activity plays a role in adaptation to increased dietary salt intake. Intrarenal arterial infusion of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) in control rats resulted in decreased glomerular filtration rate, renal vasoconstriction, natriuresis, and proteinuria. When RPP was held at basal levels with suprarenal aortic snare, L-NMMA had similar hemodynamic effects but decreased sodium excretion and did not induce proteinuria. Exposure of rats to high salt intake (1% NaCl drinking water) for 2 wk induced increased serum concentration and urinary excretion of the NO decomposition products, NO2 + NO3. Urinary NO2 + NO3 and sodium excretion were significantly correlated. Compared with controls, chronically salt-loaded rats also demonstrated enhanced renal hemodynamic responses to NO synthase inhibition. We conclude that the endogenous NO system directly modulates renal hemodynamics and sodium handling and participates in the renal adaptation to increased dietary salt intake. Enhanced NO synthesis in response to increased salt intake may facilitate sodium excretion and allow maintenance of normal blood pressure.

Neuronal Nitric Oxide Synthase Beta: A Salt-Sensitive Splice Variant Expressed in the Macula Densa

Conference Paper

Full-text available

Oct 2009

Inhibition of Nitric Oxide Synthase 1 Induces Salt-Sensitive Hypertension in Nitric Oxide Synthase 1α Knockout and Wild-Type Mice

Article

Full-text available

Feb 2016
Hypertension

We recently showed that α, β, and γ splice variants of neuronal nitric oxide synthase (NOS1) expressed in the macula densa and NOS1β accounts for most of the NO generation. We have also demonstrated that the mice with deletion of NOS1 specifically from the macula densa developed salt-sensitive hypertension. However, the global NOS1 knockout (NOS1KO) strain is neither hypertensive nor salt sensitive. This global NOS1KO strain is actually an NOS1αKO model. Consequently, we hypothesized that inhibition of NOS1β in NOS1αKO mice induces salt-sensitive hypertension. NOS1αKO and C57BL/6 wild-type (WT) mice were implanted with telemetry transmitters and divided into 7-nitroindazole (10 mg/kg/d)-treated and nontreated groups. All of the mice were fed a normal salt (0.4% NaCl) diet for 5 days, followed by a high-salt diet (4% NaCl). NO generation by the macula densa was inhibited by >90% in WT and NOS1αKO mice treated with 7-nitroindazole. Glomerular filtration rate in conscious mice was increased by ≈40% after a high-salt diet in both NOS1αKO and WT mice. In response to acute volume expansion, glomerular filtration rate, diuretic and natriuretic response were significantly blunted in the WT and knockout mice treated with 7-nitroindazole. Mean arterial pressure had no significant changes in mice fed a high-salt diet, but increased ≈15 mm Hg similarly in NOS1αKO and WT mice treated with 7-nitroindazole. We conclude that NOS1β, but not NOS1α, plays an important role in control of sodium excretion and hemodynamics in response to either an acute or a chronic salt loading.

Hormonsubstitution, Stickstoffmonoxid (NO) und kardiovaskul

Article

Jan 1998

Postmenopausal oestrogen deficiency is associated with increased incidence of cardiovascular disease and oestrogen replacement therapy markedly reduces this risk. The mechanisms, how oestrogens induce their cardioprotective effects, remain still unclear. NO (nitric oxide) could play an important role. Our investigations provide clinical evidence that 17ß-oestradiol (E 2) increases circulating nitrite/ nitrate (NO2-/NO 3-) levels, stable metabolites of NO, irrespective whether oestradiol is of endogenous or of exogenous origin, and irrespective whether E2 is administered orally or transdermally. Our data confirm the finding, that the cardioprotective effects of oestradiol are mediated at least in part through oestradiol-induced NO synthesis. Progesterone in luteal concentrations does not influence the E2 induced increase in circulating NO 2-/NO3- levels, however, the concomitant administration of an artificial progestin may attenuate the NO release. Finally, our observations also provide evidence for the existence of responders and nonresponders with respect to improvement of endogenous NO levels, suggesting that a significant number, but not all of the hormonally substituted postmenopausal women profit fully from the beneficial properties of a hormonal replacement therapy.

293 AMINOGUANIDINE ATTENUATES HYPERTENSION DEVELOPMENT BUT 7-NITROINDAZOLE EXACERBATES KIDNEY DAMAGE IN SPONTANEOUSLY HYPERTENSIVE RATS

Article

Sep 2012

Background: : Nitric oxide (NO) deficiency contributes to hypertension and end-organ damages. There are three nitric oxide synthase (NOS) isoforms have been identified: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). In spontaneously hypertensive rat (SHR), whether selective nNOS or iNOS inhibition exacerbates kidney damage remains unclear. Design and methods: At the age of 7 weeks, the SHRs were assigned into 4 groups (n = 8 for each group): group 1, SHRs without treatment; group 2 (SHR+7-NI), SHRs that received 7-nitroindazole (nNOS inhibitor) (10 mg/kg/day); group 3 (SHR+salt), SHRs that received 1% NaCl; and group 4 (SHR+AG), SHRs treated with 0.1% aminoguanidine (AG, iNOS inhibitor). All rats were sacrificed at 12 wk-old. Results: The mean arterial pressure (MAP) of SHR treated with salt was increased compared with SHRs. While AG caused decreased MAP at 8 and 12 weeks of age in SHRs. Both 7-NI and salt exacerbated kidney injury in SHRs. AG increased renal L-arginine (ARG) levels, ARG-to-ADMA ratio, and CAT-1 and ASS in the kidney. Salt treatment decreased renal nNOS-[alpha] protein level and DDAH activity. Salt and AG treatment similarly increased nNOS-[beta] protein abundance in SHR kidneys. Conclusions: AG attenuates hypertension development relates to upregulation of CIT-to-ARG conversion and increased ARG-to-ADMA ratio in SHR kidney. 7-NI impairs renal function but has no effect on BP, suggesting the renoprotection of nNOS. Salt exacerbates kidney damage mainly by decreased renal nNOS-[alpha] protein level and DDAH activity. Our findings highlight the protective role of nNOS/NO pathway in the development of kidney damage in SHRs.

THE EFFECTS OF HIGH SALT DIET AND EXERCISE ON THE WATER-SALT BALANCE AND BLOOD PRESSURE IN RATS

Article

Full-text available

Feb 2021

In the study which was prepared based on the factors that can take place in essential hypertension pathology; We aimed to investigate the interactions of intensive exercise, high salt and partial NOS inhibition applications with each other, the effects on water-salt balance and blood pressure, changes in the intrarenal dopaminergic system, which is an important natriuretic system, and the participation of oxidative stress. The rats were given intensive exercise on a treadmill at a speed of 25 m / min at 5% inclination for 30 minutes a day, LNNA at a concentration of 50 mg / L and a high salt diet of 4% for 7 days either separately or together. Blood pressures of the rats were measured on the first and last days of the experiment, and the rats were taken into metabolic cages; 24-hour water intake and urinevolume were measured. Dopamine levels were measured in 24-hour urine to detect intrarenal dopamine synthesis. In addition, oxidative stress parameters in the serums of rats; TAS, TOS and OSI levels were measured. Blood pressure was found to be high in the groups in which intensive exercise was applied together with LNNA and high salt diet. While there was no change in the water balance of this group, it was found that sodium excretion and dopamine levels increased in 24-hour urine. In addition, it was found that the total oxidant status increased in this group, and oxidative stress developed as a result of insufficient antioxidant system. It suggests that the reason of hypertension that develops with the application of intensive exercise together with LNNA and high salt diet may be due to the vascular resistance increasing effect of oxidative stress rather than water-salt retention and it points out the necessity of studies to fully detect vascular tissue oxidative stress markers and vascular oxidative damage.

Regulation of carbohydrate metabolism by nitric oxide and hydrogen sulfide: Implications in diabetes

Article

Full-text available

Jan 2020
BIOCHEM PHARMACOL

Nitric oxide (NO) and hydrogen sulfide (H2S) are two gasotransmitters that are produced in the human body and have a key role in many of the physiological activities of the various organ systems. Decreased NO bioavailability and deficiency of H2S are involved in the pathophysiology of type 2 diabetes and its complications. Restoration of NO levels have favorable metabolic effects in diabetes. The role of H2S in pathophysiology of diabetes is however controversial; H2S production is decreased during development of obesity, diabetes, and its complications, suggesting the potential therapeutic effects of H2S. On the other hand, increased H2S levels disturb the pancreatic β-cell function and decrease insulin secretion. In addition, there appear to be important interactions between NO and H2S at the levels of both biosynthesis and signaling pathways, yet clear an insight into this relationship is lacking. H2S potentiates the effects of NO in the cardiovascular system as well as NO release from its storage pools. Likewise, NO increases the activity and the expression of H2S-generating enzymes. Inhibition of NO production leads to elimination/attenuation of the cardioprotective effects of H2S. Regarding the increasing interest in the therapeutic applications of NO or H2S-releasing molecules in a variety of diseases, particularly in the cardiovascular disorders, much is to be learned about their function in glucose/insulin metabolism, especially in diabetes. The aim of this review is to provide a better understanding of the individual and the interactive roles of NO and H2S in carbohydrate metabolism.

Perinatal iron deficiency combined with a high salt diet in adulthood causes sex‐dependent vascular dysfunction in rats

Article

Full-text available

Aug 2019
J PHYSIOL-LONDON

Key points Perinatal iron deficiency causes changes in offspring mesenteric artery function in adulthood, particularly in males, which can be exacerbated by chronic intake of a high salt diet. Perinatal iron deficient male offspring exhibit enhanced conversion of big endothelin‐1 to active endothelin‐1, coinciding with decreased nitric oxide levels. Perinatal iron deficient male offspring have reduced nitric oxide‐mediated endothelial‐dependent vasodilatation coincident with increased vascular superoxide levels following consumption of a high salt diet. Perinatal iron deficiency has no apparent effects on vascular function in female offspring, even when fed a high salt diet. These results help us better understand underlying vascular mechanisms contributing to increased cardiovascular risk from perinatal stressors such as iron deficiency. Abstract Pre‐ and immediate postnatal stressors, such as iron deficiency, can alter developmental trajectories and predispose offspring to long‐term cardiovascular dysfunction. Here, we investigated the impact of perinatal iron deficiency on vascular function in the adult offspring, and whether these long‐term effects were exacerbated by prolonged consumption of a high salt diet in adulthood. Female Sprague Dawley rats were fed either an iron‐restricted or ‐replete diet prior to and throughout pregnancy. Six weeks prior to experimentation at 6 months of age, adult offspring were fed either a normal or high salt diet. Mesenteric artery responses to vasodilators and vasoconstrictors were assessed ex vivo by wire myography. Male perinatal iron deficient offspring exhibited decreased reliance on nitric oxide with methacholine‐induced vasodilatation (interaction P = 0.03), coincident with increased superoxide levels when fed the high salt diet (P = 0.01). Male perinatal iron deficient offspring exhibit enhanced big endothelin‐1 conversion to active endothelin‐1 (P = 0.02) concomitant with decreased nitric oxide levels (P = 0.005). Female offspring vascular function was unaffected by perinatal iron deficiency, albeit the high salt diet was associated with impaired vasodilation and decreased nitric oxide production (P = 0.02), particularly in the perinatal iron deficient offspring. These findings implicate vascular dysfunction in the sex‐specific programming of cardiovascular dysfunction in the offspring by perinatal iron deficiency.

Multilayered Interplay Between Fructose and Salt in Development of Hypertension: What Has Been Revealed So Far

Article

Dec 2018

Nitric oxide mediates anomalous tubuloglomerular feedback in rats fed high NaCl diet after subtotal nephrectomy

Article

Oct 2018

Scott C Thomson

Tubuloglomerular feedback (TGF) responses become anomalous in rats fed high NaCl diet after subtotal nephrectomy (STN) such that stimulating TGF causes single nephron GFR (SNGFR) to increase rather than decrease. Micropuncture experiments were performed to determine whether this anomaly results from heightened nitric oxide response to distal delivery, which is a known mechanism for resetting TGF, or from connecting tubule TGF (cTGF), which is a novel amiloride-inhibitable system for offsetting TGF responses. Micropuncture was done in Wistar Froemter rats fed high NaCl diet (HS) for 8-10 days after STN or sham nephrectomy. TGF was manipulated by orthograde microperfusion of Henle's loop with artificial tubular fluid with or without NOS inhibitor, LNMMA, or the cell-impermeant amiloride analog, benzamil. SNGFR was measured by inulin clearance in tubular fluid collections from the late proximal tubule. TGF responses were quantified as the increase in SNGFR that occurred when the perfusion rate was reduced from 50 to 8 nl/min in STN or 40 to 8 nl/min in shams. The baseline TGF response was anomalous in STN HS (-4±3 vs 14±3 nl/min, P<0.001). TGF response was normalized by perfusing STN nephron with LNMMA (14±3 nl/min, p<0.005 for ANOVA cross term) but not with benzamil (-3±4 nl/min, p=0.4 for ANOVA cross term). Anomalous TGF occurs in STN HS due to heightened effect of tubular flow on nitric oxide signaling, which increases to the point of overriding the normal TGF response. There is no role for cTGF in this phenomenon.

Sodium intake but not renal nerves attenuates renal venous pressure-induced changes in renal hemodynamics in rats

Article

Jun 2018

Increased central venous pressure and renal venous pressure (RVP) is associated with worsening of renal function in acute exacerbation of congestive heart failure. We tested whether an acute, isolated elevation of RVP in one kidney leads to ipsilateral renal vasoconstriction and decreased GFR and whether this depends on dietary salt intake or activation of renal nerves. Male Lewis rats received a normal (1% NaCl, NS) or high salt diet (6% NaCl, HS) for {greater than or equal to}14 days before the acute experiment. Rats were then randomized into 3 groups: time control and RVP elevation to either 10 or 20 mmHg to assess heart rate, renal blood flow (RBF) and GFR. To increase RVP, the left renal vein was partially occluded for 120 min. To determine the role of renal nerves, surgical denervation was conducted in rats on both diets. RSNA was additionally recorded in a separate group of rats. Increasing RVP to 20 mmHg decreased ipsilateral RBF (7.5{plus minus}0.4 to 4.1{plus minus}0.7 ml/min, p<0.001) and renal vascular conductance (0.082{plus minus}0.006 to 0.060{plus minus}0.011 ml/min•mmHg, p<0.05) and GFR (1.28{plus minus}0.08 to 0.40{plus minus}0.13 ml/min, p<0.05) in NS rats. The reduction was abolished by high salt diet but not by renal denervation. Furthermore, a major increase of RVP (1.6{plus minus}0.8 to 24.7{plus minus}1.2 mmHg) immediately suppressed RSNA and decreased heart rate (p<0.05), which points to suppression of both local and systemic sympathetic activity. Taken together, acute elevated RVP induces renal vasoconstriction and decreased GFR, which is more likely to be mediated via the renin-angiotensin system (RAS) than via renal nerves.

Free radical scavenging reverses fructose-induced salt-sensitive hypertension

Article

Full-text available

Dec 2017

Zachary P Zenner, Kevin L Gordish, William H Beierwaltes Department of Internal Medicine, Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI, USA Abstract: We have previously reported that a moderate dietary supplementation of 20% fructose but not glucose leads to a salt-sensitive hypertension related to increased proximal sodium–hydrogen exchanger activity and increased renal sodium retention. We also found that while high salt increased renal nitric oxide formation, this was retarded in the presence of fructose intake. We hypothesized that at least part of the pathway leading to fructose-induced salt-sensitive hypertension could be due to fructose-induced formation of reactive oxygen species and inappropriate stimulation of renin secretion, all of which would contribute to an increase in blood pressure. We found that both 20% fructose intake and a high-salt diet stimulated 8-isoprostane excretion. The superoxide dismutase (SOD) mimetic tempol significantly reduced this elevated excretion. Next, we placed rats on a high-salt diet (4%) for 1 week in combination with normal rat chow or 20% fructose with or without chronic tempol administration. A fructose plus high-salt diet induced a rapid increase (15 mmHg) in systolic blood pressure and reversed high salt suppression of plasma renin activity. Tempol treatment reversed the pressor response and restored high salt suppression of renin. We conclude that fructose-induced salt-sensitive hypertension is driven by increased renal reactive oxygen species formation associated with salt retention and an enhanced renin–angiotensin system. Keywords: reactive oxygen species, tempol, sodium, renin, oxidative stress

Long-Term High Salt Intake Involves Reduced SK Currents and Increased Excitability of PVN Neurons with Projections to the Rostral Ventrolateral Medulla in Rats

Article

Full-text available

Dec 2017
Neural Plast

Evidence indicates that high salt (HS) intake activates presympathetic paraventricular nucleus (PVN) neurons, which contributes to sympathoexcitation of salt-sensitive hypertension. The present study determined whether 5 weeks of HS (2% NaCl) intake alters the small conductance Ca ²⁺ -activated potassium channel (SK) current in presympathetic PVN neurons and whether this change affects the neuronal excitability. In whole-cell voltage-clamp recordings, HS-treated rats had significantly decreased SK currents compared to rats with normal salt (NS, 0.4% NaCl) intake in PVN neurons. The sensitivity of PVN neuronal excitability in response to current injections was greater in HS group compared to NS controls. The SK channel blocker apamin augmented the neuronal excitability in both groups but had less effect on the sensitivity of the neuronal excitability in HS group compared to NS controls. In the HS group, the interspike interval (ISI) was significantly shorter than that in NS controls. Apamin significantly shortened the ISI in NS controls but had less effect in the HS group. This data suggests that HS intake reduces SK currents, which contributes to increased PVN neuronal excitability at least in part through a decrease in spike frequency adaptation and may be a precursor to the development of salt-sensitive hypertension.

Nitric oxide production by glomerular podocytes

Article

Nov 2017

Nitric Oxide (NO), a potent vasodilator and vital signaling molecule, has been shown to contribute to the regulation of glomerular ultrafiltration. However, whether changes in NO occur in podocytes during the pathogenesis of salt-sensitive hypertension has not yet been thoroughly examined. We showed here that podocytes produce NO, and further hypothesized that hypertensive animals would exhibit reduced NO production in these cells in response to various paracrine factors, which might contribute to the damage of glomeruli filtration barrier and development of proteinuria. To test this, we isolated glomeruli from the kidneys of Dahl salt-sensitive (SS) rats fed a low salt (LS; 0.4% NaCl) or high salt (HS; 4% NaCl, 3 weeks) diets and loaded podocytes with either a combination of NO and Ca(2+) fluorophores (DAF-FM and Fura Red, respectively) or DAF-FM alone. Changes in fluorescence were observed with confocal microscopy in response to adenosine triphosphate (ATP), angiotensin II (Ang II), and hydrogen peroxide (H2O2). Application of Ang II resulted in activation of both NO and intracellular calcium ([Ca(2+)]i) transients. In contrast, ATP promoted [Ca(2+)]i transients, but did not have any effects on NO production. SS rats fed a HS diet for 3 weeks demonstrated impaired NO production: the response to Ang II or H2O2 in podocytes of glomeruli isolated from SS rats fed a HS diet was significantly reduced compared to rats fed a LS diet. Therefore, glomerular podocytes from hypertensive rats showed a diminished NO release in response to Ang II or oxidative stress, suggesting that podocytic NO signaling is dysfunctional in this condition and likely contributes to the development of kidney injury.

Understanding the Two Faces of Low-Salt Intake

Article

Full-text available

May 2017
Curr Hypertens Rep

Fierce debate has developed whether low-sodium intake, like high-sodium intake, could be associated with adverse outcome. The debate originates in earlier epidemiological studies associating high-sodium intake with high blood pressure and more recent studies demonstrating a higher cardiovascular event rate with both low- and high-sodium intake. This brings into question whether we entirely understand the consequences of high- and (very) low-sodium intake for the systemic hemodynamics, the kidney function, the vascular wall, the immune system, and the brain. Evolutionarily, sodium retention mechanisms in the context of low dietary sodium provided a survival advantage and are highly conserved, exemplified by the renin-angiotensin system. What is the potential for this sodium-retaining mechanism to cause harm? In this paper, we will consider current views on how a sodium load is handled, visiting aspects including the effect of sodium on the vessel wall, the sympathetic nervous system, the brain renin-angiotensin system, the skin as “third compartment” coupling to vascular endothelial growth factor C, and the kidneys. From these perspectives, several mechanisms can be envisioned whereby a low-sodium diet could potentially cause harm, including the renin-angiotensin system and the sympathetic nervous system. Altogether, the uncertainties preclude a unifying model or practical clinical guidance regarding the effects of a low-sodium diet for an individual. There is a very strong need for fundamental and translational studies to enhance the understanding of the potential adverse consequences of low-salt intake as an initial step to facilitate better clinical guidance.

Moderate (20%) fructose‐enriched diet stimulates salt‐sensitive hypertension with increased salt retention and decreased renal nitric oxide

Article

Full-text available

Apr 2017

Previously, we reported that 20% fructose diet causes salt-sensitive hypertension. In this study, we hypothesized that a high salt diet supplemented with 20% fructose (in drinking water) stimulates salt-sensitive hypertension by increasing salt retention through decreasing renal nitric oxide. Rats in metabolic cages consumed normal rat chow for 5 days (baseline), then either: (1) normal salt for 2 weeks, (2) 20% fructose in drinking water for 2 weeks, (3) 20% fructose for 1 week, then fructose + high salt (4% NaCl) for 1 week, (4) normal chow for 1 week, then high salt for 1 week, (5) 20% glucose for 1 week, then glucose + high salt for 1 week. Blood pressure, sodium excretion, and cumulative sodium balance were measured. Systolic blood pressure was unchanged by 20% fructose or high salt diet. 20% fructose + high salt increased systolic blood pressure from 125 ± 1 to 140 ± 2 mmHg (P < 0.001). Cumulative sodium balance was greater in rats consuming fructose + high salt than either high salt, or glucose + high salt (114.2 ± 4.4 vs. 103.6 ± 2.2 and 98.6 ± 5.6 mEq/Day19; P < 0.05). Sodium excretion was lower in fructose + high salt group compared to high salt only: 5.33 ± 0.21 versus 7.67 ± 0.31 mmol/24 h; P < 0.001). Nitric oxide excretion was 2935 ± 256 μmol/24 h in high salt-fed rats, but reduced by 40% in the 20% fructose + high salt group (2139 ± 178 μmol /24 hrs P < 0.01). Our results suggest that fructose predisposes rats to salt-sensitivity and, combined with a high salt diet, leads to sodium retention, increased blood pressure, and impaired renal nitric oxide availability.

Novel Paradigms of Salt and Hypertension

Article

Feb 2017

Salt resistance/sensitivity refers specifically to the effect of dietary sodium chloride (salt) intake on BP. Increased dietary salt intake promotes an early and uniform expansion of extracellular fluid volume and increased cardiac output. To compensate for these hemodynamic changes and maintain constant BP in salt resistance, renal and peripheral vascular resistance falls and is associated with an increase in production of nitric oxide. In contrast, the decline in peripheral vascular resistance and the increase in nitric oxide are impaired or absent in salt sensitivity, promoting an increase in BP in these individuals. Endothelial dysfunction may pose a particularly significant risk factor in the development of salt sensitivity and subsequent hypertension. Vulnerable salt-sensitive populations may have in common underlying endothelial dysfunction due to genetic or environmental influences. These individuals may be very sensitive to the hemodynamic stress of increased effective blood volume, setting in motion untoward molecular and biochemical events that lead to overproduction of TGF-β, oxidative stress, and limited bioavailable nitric oxide. Finally, chronic high-salt ingestion produces endothelial dysfunction, even in salt-resistant subjects. Thus, the complex syndrome of salt sensitivity may be a function of the endothelium, which is integrally involved in the vascular responses to high salt intake.

Renal sodium handling in experimental diabetes: role of NO

Article

Nov 1996

Recent studies have suggested that diabetes is a state of increased renal nitric oxide (NO) activity as assessed by urinary excretion of nitrites and nitrates (NO x ), and that NO synthase inhibitors reverse the increased glomerular filtration rate (GFR) observed in experimental diabetes. In addition to being a potent vasodilator in the renal vasculature, NO also plays a role in modulation of renal sodium excretion. To explore the role of NO in diabetes-associated alterations in renal excretory function, renal haemodynamic and sodium handling parameters were evaluated in conscious control (C) and streptozotocin diabetic rats (D) and correlated to the renal activity of NO, as assessed by urinary excretion of its metabolites NO x . To further explore this issue, the changes in renal haemodynamics and sodium handling were also assessed after NO synthase inhibition with a non-pressor dose of L-nitro-arginine-methyl-ester (L-NAME) and after administration of the NO donor, glyceryl trinitrate (GTN). Systolic blood pressure was not different between C and D rats. D rats exhibited marked hyperglycaemia ( P <0.001), and increases in GFR ( P <0.001), renal plasma flow, filtration fraction, urinary sodium excretion (U Na V, P <0.001), filtered load of sodium (FL Na , P <0.01), and a decrease in fractional reabsorption of sodium (FR Na , P <0.0001). In contrast, total reabsorption of sodium (TR Na ) was increased in D rats compared to C rats ( P <0.0001). The urinary excretion of NO was markedly increased in D rats ( P <0.01). Regression analyses performed in D rats revealed a close relationship between U Na V and GFR and a weaker correlation with urinary NO x . Although FR Na correlated only with urinary excretion of NO x , there was a strong relationship between TR Na and GFR. In contrast to D rats, control rats demonstrated only a relationship between TR Na and GFR and no other correlations were found, in D rats, NO inhibition with L-NAME (1 mg/kg body weight) resulted in a marked decrease in GFR and urinary NO x associated with decreases in FL Na and TR Na but did not influence FR Na . In contrast, in C rats the post-L-NAME decrease in NO x was not associated with significant changes in GFR and renal sodium handling. GTN-treated C rats exhibited a renal vasodilatory response and an increase in natriuresis and urinary NO x whereas no renal changes were observed in D rats during GTN administration. The present data indicate that changes in renal sodium handling before and after NO modulation in experimental diabetes are related to changes in GFR rather than to the renal activity of NO. Therefore, in contrast to the effects on renal haemodynamics, NO does not play an important role in the altered renal sodium handling observed in experimental diabetes.

Systemic vascular adaptation to increases in blood volume: the role of the blood-vessel wall

Article

Feb 1996

Transforming Growth Factor-β Mediates Endothelial Dysfunction in Rats During High Salt Intake

Article

Full-text available

Oct 2015
AM J PHYSIOL-RENAL

Endothelial dysfunction has been shown to be predictive of subsequent cardiovascular events and death. Through a mechanism that is incompletely understood, increased dietary salt intake promotes endothelial dysfunction in healthy, salt-resistant humans. The present study tested the hypothesis that dietary salt-induced TGF-β promoted endothelial dysfunction and salt-dependent changes in blood pressure (BP). Sprague-Dawley rats receiving diets containing 0.3% NaCl (LS) or 8.0% NaCl (HS) were treated with vehicle or SB525334 (SB), a specific inhibitor of TGF-β receptor I/activin receptor-like kinase 5 (ALK5), beginning on day 5. BP was monitored using radio-telemetry in the four groups of rats (LS, LS SB, HS, and HS SB) for up to 14 days. By day 14 of the study, mean daytime systolic blood pressure (SBP) and mean pulse pressure (PP) of the HS group treated with vehicle was greater than the other three groups; mean daytime SBP and PP of the HS SB group did not differ from the LS and LS SB groups. While mean SBP, DBP and MAP did not differ among the groups on the 7th day of the study, endothelium-dependent vasorelaxation was impaired specifically in the HS group; treatment with the ALK5 inhibitor prevented the high dietary salt intake-induced increases in phospho-Smad2 (S465/467) and NADPH oxidase-4 in endothelial lysates and normalized endothelial function. These findings suggest that high salt-induced endothelial dysfunction and the development of salt-dependent increases in BP were related to endothelial TGF-β signaling.

Species differences in regulation of renal proximal tubule transport by certain molecules

Article

Full-text available

May 2015

Renal proximal tubules (PTs) play important roles in the regulation of acid/base, plasma volume and blood pressure. Recent studies suggest that there are substantial species differences in the regulation of PT transport. For example, thiazolidinediones (TZDs) are widely used for the treatment of type 2 diabetes mellitus, but the use of TZDs is associated with fluid overload. In addition to the transcriptional enhancement of sodium transport in distal nephrons, TZDs rapidly stimulate PT sodium transport via a non-genomic mechanism depending on peroxisome proliferator activated receptor γ/Src/epidermal growth factor receptor (EGFR)/MEK/ERK. In mouse PTs, however, TZDs fail to stimulate PT transport probably due to constitutive activation of Src/EGFR/ERK pathway. This unique activation of Src/ERK may also affect the effect of high concentrations of insulin on mouse PT transport. On the other hand, the effect of angiotensin II (Ang II) on PT transport is known to be biphasic in rabbits, rats, and mice. However, Ang II induces a concentration-dependent, monophasic transport stimulation in human PTs. The contrasting responses to nitric oxide/guanosine 3',5'-cyclic monophosphate pathway may largely explain these different effects of Ang II on PT transport. In this review, we focus on the recent findings on the species differences in the regulation of PT transport, which may help understand the species-specific mechanisms underlying edema formation and/or hypertension occurrence.

Dietary salt regulates epithelial sodium channels in rat endothelial cells: adaptation of vasculature to salt: Dietary salt regulates endothelial epithelial sodium channels

Article

Full-text available

May 2015
BRIT J PHARMACOL

The epithelial sodium channel (ENaC) is expressed in vascular endothelial cells and is a negative modulator of vasodilation. However, the role of endothelial ENaC in salt-sensitive hypertension remains unclear. We would investigate how endothelial ENaC responds to high-salt (HS) challenge in Sprague-Dawley (SD) rat. The blood pressure (BP) and plasma aldosterone levels were measured. We used patch-clamp technique to record ENaC, for the first time, in split-open mesenteric arteries (MAs). Western blot and Griess assay were used to detect expression of α-ENaC, eNOS and nitric oxide (NO). Vasodilatation in 2(nd) -order MAs was measured with wire myograph assays. Functional ENaC was observed in endothelial cells, and its activity was significantly decreased one week after HS diet. Three weeks after HS diet, ENaC expression was also reduced. When either ENaC activity or expression was reduced, endothelium-dependent relaxation (EDR) of MAs was enhanced, as tested by acetylcholine (ACh), and this enhancement of EDR was mimicked by amiloride, an ENaC blocker. On the other hand, HS diet significantly increased contractility of MAs, due to the decreased eNOS activity and NO levels; however, ACh-induced percent increment of NO was much higher in MAs isolated from HS rats compared to that from NS rats. HS intake significantly increased the BP of SD rats, but simultaneously enhanced EDR by reducing ENaC activity and expression due to the feedback inhibition. Therefore, ENaC may play an important role in endothelial cells for vasculature to adapt to HS challenge. This article is protected by copyright. All rights reserved.

Angiotensin AT2 receptor agonist prevents salt-sensitive hypertension in obese Zucker rats

Article

Full-text available

Jun 2015
AM J PHYSIOL-RENAL

High sodium intake is a risk factor for the pathogenesis of hypertension, especially in obesity. The present study is designed to investigate whether angiotensin type-2 receptor activation with selective agonist C21 prevents high-sodium diet (HSD)-induced hypertension in obese animals. Male obese rats were treated with AT2R agonist C21 (1 mg/kg/day, oral) while maintained on either normal-sodium diet (NSD, 0.4%) or HSD (4%) for 2-weeks. Radio-telemetric recording showed a time dependent increase in systolic blood pressure in HSD-fed obese rats, being maximal increase (~27 mmHg) at day 12 of the HSD regimen. C21 treatment completely prevented the increase in blood pressure of HSD-fed rats. Compared to NSD controls, HSD-fed obese rats had greater natriuresis/diuresis and urinary levels of nitrates, and these parameters were further increased by C21 treatment. HSD-fed rats expressed higher level of cortical AngII, which was reduced to 50% by C21 treatment. HSD feeding and/or C21 treatment had no effects on cortical renin activity and the expression of angiotensin converting enzyme and chymase, which are AngII producing enzymes. However, Ang(1-7) concentration and ACE2 activity in the renal cortex were reduced by HSD feeding, and C21 treatment rescued both the parameters. Also, C21 treatment reduced the cortical expression of AT1R in HSD-fed rats, but had no effect of AT2R expression. We conclude that chronic treatment with the AT2R agonist C21 prevents salt-sensitive hypertension in obese rats, and a reduction in the renal AngII/AT1R and enhanced ACE2/Ang(1-7) levels may play a potential role in this phenomenon. Copyright © 2015, American Journal of Physiology - Renal Physiology.

Expression of (pro)renin receptor and its upregulation by high salt intake in the rat nephron

Article

Dec 2014

Regulatory roles of nitric oxide and angiotensin II on renal tubular transport

Article

Full-text available

Nov 2014

Renal tubules regulate blood pressure and humoral homeostasis. Mediators that play a significant role in regulating the transport of solutes and water include angiotensin II (AngII) and nitric oxide (NO). AngIIcan significantly raise blood pressure via effects on the heart, vasculature, and renal tubules. AngII generally stimulates sodium reabsorption by triggering sodium and fluid retention in almost all segments of renal tubules. Stimulation of renal proximal tubule (PT) transport is thought to be essential for AngII-mediated hypertension. However, AngII has a biphasic effect on in vitro PT transport in mice, rats, and rabbits: stimulation at low concentrations and inhibition at high concentrations. On the other hand, NO is generally thought to inhibit renal tubular transport. In PTs, NO seems to be involved in the inhibitory effect of AngII. A recent study reports a surprising finding: AngII has a monophasic stimulatory effect on human PT transport. Detailed analysis of signalling mechanisms indicates that in contrast to other species, the human NO/guanosine 3',5'-cyclic monophosphate/extracellular signal-regulated kinase pathway seems to mediate this effect of Ang II on PT transport. In this review we will discuss recent progress in understanding the effects of AngII and NO on renal tubular transport.

Nitric Oxide and Inflammatory Bowel Disease: Evidence for Local Intestinal Production in Children with Active Colonic Disease

Article

Jan 1998

Background Active colitis in patients with inflammatory bowel disease is associated with mucosal vasodilation, increased intestinal permeability and abnormal colonic motility. Nitric oxide is a messenger molecule with many functions, including regulation of local blood flow, vasomotor tone, and inflammation. Increased nitric oxide production and inducible nitric oxide synthase activity have been demonstrated in experimental models of colitis. This study was designed to determine the relationship between nitric oxide production and colonic inflammation in children with active colitis and in control subjects and whether expression of inducible nitric oxide synthase protein is demonstrable in the intestinal epithelium of these patients. Methods Nitrate + nitrite were measured in urine, stool, and plasma using the Griess assay. Expression of inducible nitric oxide synthase protein in intestinal tissue was determined by immunohistochemical localization. Results Urinary nitrate + nitrite levels were not significantly different in patients and control subjects. In contrast, stool and plasma nitrate + nitrite concentrations were significantly higher in children with inflammatory bowel disease compared with levels in control children (stool: 162.4 ± 31.0μmol/l versus 77.2 ± 22.1 μmol/l; plasma 65.2 ± 9.9μmol/l versus 38.1 ± 6.6 μmol/L; p < 0.05). Stool nitrate + nitrite levels significantly correlated with plasma values. Immunohistochemical staining of colonic tissue from children with inflammatory bowel disease demonstrated inducible nitric oxide synthase protein located exclusively in epithelial cells. Conclusion Increased nitric oxide production and enhanced intestinal epithelial cell expression of inducible nitric oxide synthase protein are associated with active colonic inflammation.

DIURETIC ACTIVITY OF CAROB (CERATONIA SILIQUA L.) HONEY: COMPARISON WITH FUROSEMIDE

Article

Full-text available

Jun 2015

Background: Honey has wide range of biological activities. It has effect on renal function, and urinary nitric oxide and prostaglandins level. The present study was conducted to evaluate diuretic potential of carob honey, collected from Morocco, in normal rats and the results were compared with use of furosemide. Materials and methods: Adult male Wister rats weighing between 230 and 278 g were used. The animals were divided into three groups; group 1 received oral administration of distilled water (10 ml/kg BW), and served as control group, group 2 received oral administration of furosemide (10 mg/kg BW), and group 3 was treated with oral administration of carob honey (100 mg/kg BW). Urine volume, and urine and plasma sodium and potassium were measured after single dose of the interventions and after daily administrations of the interventions. Results: After the single dose of carob honey, urine output was significantly increased at all time intervals (1-6 hrs and at 24 hrs after administration). The daily dose of carob honey for nine days significantly increased urine volume as compared to control group. Carob honey increased urinary levels of sodium and potassium, and did not cause hypokalemia, while furosemide increased urinary sodium and potassium and caused hypokalemia. Conclusion: Carob honey has diuretic, natriuretic and kaliuretic activity without side effects of hypokalemia that was observed with use of furosemide.

The effects of renal dopaminergic system on the development of hypertension with high salt diet and L-NNA administration

Article

Jun 2023

Objective: We aimed to investigate the intrarenal dopamine synthesis efficiency, blood pressure changes and the effects of this system on hypertension developed by NOS inhibition and high salt diet. Method: Wistar Albino male rats were administered water containing 50mg/L or 100mg/L concentrations of L-NNA, standard rat feed containing 0.8%salt, or 4%high salt alone or with L-NNA for 7days. Blood pressure measurements were made with the tail-cuff method. 24-hour water intake and urine volume were also measured. Results: Administration of L-NNA or high-salt diet alone for 7days did not cause a change in blood pressure, while their combined administration resulted in a significant increase in blood pressure. Blood pressures were found to be higher in the L-NNA100+HS group compared to the other groups. While the amount of water intake in 24hours did not change, the amount of 24-hour urine was reduced. 24-hour urinary sodium excretion, sodium clearance and GFR was decreased, and 24-hour urine dopamine concentrations were increased. Conclusion: Co-administration of nitric-oxide inhibitor and high-salt diet failed to prevent renal dopaminergic system blood pressure increase. Despite the increase in dopamine synthesis, intrarenal dopamine activity could not be realized by receptor interaction and it is thought that the increase in blood pressure is caused by the development of renal oxidative stress.

The Role of Macula Densa Nitric Oxide Synthase 1 Beta Splice Variant in Modulating Tubuloglomerular Feedback

Chapter

Jan 2023

Abnormalities in renal electrolyte and water excretion may result in inappropriate salt and water retention, which facilitates the development and maintenance of hypertension, as well as acid-base and electrolyte disorders. A key mechanism by which the kidney regulates renal hemodynamics and electrolyte excretion is via tubuloglomerular feedback (TGF), an intrarenal negative feedback between tubules and arterioles. TGF is initiated by an increase of NaCl delivery at the macula densa cells. The increased NaCl activates luminal Na-K-2Cl cotransporter (NKCC2) of the macula densa cells, which leads to activation of several intracellular processes followed by the production of paracrine signals that ultimately result in a constriction of the afferent arteriole and a tonic inhibition of single nephron glomerular filtration rate. Neuronal nitric oxide (NOS1) is highly expressed in the macula densa. NOS1β is the major splice variant and accounts for most of NO generation by the macula densa, which inhibits TGF response. Macula densa NOS1β-mediated modulation of TGF responses plays an essential role in control of sodium excretion, volume and electrolyte hemostasis, and blood pressure. In this article, we describe the mechanisms that regulate macula densa-derived NO and their effect on TGF response in physiologic and pathologic conditions. © 2023 American Physiological Society. Compr Physiol 13:4215-4229, 2023.

Activation of TRPV1 improves natriuresis and salt sensitivity in high-fat diet fed mice

Article

Jul 2022
BIOCHEM PHARMACOL

Western diet (WD) intake increases morbidity of obesity and salt-sensitive hypertension albeit mechanisms are largely unknown. We investigated the role of transient receptor potential vanilloid 1 (TRPV1) in WD intake-induced hypertension. TRPV1-/- and wild-type (WT) mice were fed a normal (CON) or Western diet (WD) for 16-18 weeks. Mean arterial pressure (MAP) after normal sodium glucose (NSG) loading with or without L-NAME (a NO synthase inhibitor) or N-oleoyldopamine (OLDA, a TRPV1 agonist) was not different between the two strains on CON. WT or TRPV1-/- mice fed WD had increased MAP after NSG, with a greater magnitude in TRPV1-/- mice. OLDA decreased while L-NAME increased MAP in WT-WD but not in TRPV1-/--WD mice. The urinary nitrates plus nitrites excretion (UNOx), an indicator of renal NO production, was increased in both strains on CON after NSG. TRPV1 ablation with WD intake abolished NSG-induced increment in UNOx. OLDA further increased while L-NAME prevented NSG-induced increment in UNOx in WT-WD mice. Urinary sodium excretion was increased in both strains on CON and in WT-WD mice but not in TRPV1-/--WD mice after NSG. OLDA further increased while L-NAME prevented NSG-induced increases in sodium excretion in WT-WD but not in TRPV1-/--WD mice. Thus, TRPV1 ablation increases salt sensitivity during WD intake possibly via impaired renal NO production and sodium excretion. Activation of TRPV1 enhances renal NO production and sodium excretion, resulting in prevention of increased salt sensitivity during WD intake.

Acute beetroot juice supplementation does not attenuate knee extensor exercise muscle fatigue in a healthy young population

Article

Full-text available

Mar 2019

Purpose: The effect of acute nitrate supplementation on muscle fatigue is largely unknown. This study aimed to evaluate the effect of acute nitrate supplementation on muscle fatigue. Methods: Thirty-five recreationally active subjects consumed 140 ml of beetroot (BR) juice (nitrate: 8 mmol·d-1) or placebo (PL) 12 and 2.5 hours before two exercise sessions. Peak torque was measured during 50 repetitions, at maximal effort, and during concentric knee extensions at 90°·s-1. Blood pressure (BP) was recorded pre- and post-exercise. Results: Peak torque, maximum work, rate of fatigue, and rate of work fatigue were similar between the BR and PL conditions. Post-exercise diastolic BP (BR: 67.2 ± 9.8 vs. PL: 64.5 ± 7.9 mmHg, p < 0.05) and mean arterial pressure (BR: 91.6 ± 9.3 vs. PL: 88.8 ± 8.2 mmHg, p < 0.05) were higher with BR supplementation. Conclusion: These findings suggest that the acute intake of BR juice had no effect on knee extensor muscle strength or fatigue but increased BP in a healthy recreationally active population.

VEGF-C attenuates renal damage in salt-sensitive hypertension: BEAINI et al.

Article

Oct 2018

Salt‐sensitive hypertension is a major risk factor for renal impairment leading to chronic kidney disease. High‐salt diet leads to hypertonic skin interstitial volume retention enhancing the activation of the tonicity‐responsive enhancer‐binding protein (TonEBP) within macrophages leading to vascular endothelial growth factor C (VEGF‐C) secretion and NOS3 modulation. This promotes skin lymphangiogenesis and blood pressure regulation. Whether VEGF‐C administration enhances renal and skin lymphangiogenesis and attenuates renal damage in salt‐sensitive hypertension remains to be elucidated. Hypertension was induced in BALB/c mice by a high‐salt diet. VEGF‐C was administered subcutaneously to high‐salt‐treated mice as well as control animals. Analyses of kidney injury, inflammation, fibrosis, and biochemical markers were performed in vivo. VEGF‐C reduced plasma inflammatory markers in salt‐treated mice. In addition, VEGF‐C exhibited a renal anti‐inflammatory effect with the induction of macrophage M2 phenotype, followed by reductions in interstitial fibrosis. Antioxidant enzymes within the kidney as well as urinary RNA/DNA damage markers were all revelatory of abolished oxidative stress under VEGF‐C. Furthermore, VEGF‐C decreased the urinary albumin/creatinine ratio and blood pressure as well as glomerular and tubular damages. These improvements were associated with enhanced TonEBP, NOS3, and lymphangiogenesis within the kidney and skin. Our data show that VEGF‐C administration plays a major role in preserving renal histology and reducing blood pressure. VEGF‐C might constitute an interesting potential therapeutic target for improving renal remodeling in salt‐sensitive hypertension.

Nitric oxide as a mediator of hemodynamic disturbances in acute renal failure associated with sepsis

Chapter

Jan 1998

Marina Noris

Sepsis remains a leading cause of acute renal failure (ARF) and contributes substantially to patient morbidity and mortality [1, 2]. Renal dysfunction in this setting is usually associated with persistent oliguria and reduced creatinine clearance [3–5] due to an impaired glomerular filtration [3] that has been documented consistently in experimental animals with endotoxemia [6–8] as well as in septic patients [2, 3]. The association of ARF in the course of sepsis with cardiopulmonary failure suggests that systemic hemodynamic factors, leading to severe and persistent renal hypoperfusion, play a key role in the reduction in glomerular filtration rate. The main cardiovascular feature of septic shock is a decrease in peripheral vascular resistance, causing a reduction in mean arterial pressure and a secondary increase in cardiac output [9]. If peripheral vasodilatation causes sufficient venous pooling to impair cardiac preload, cardiac output will decline, further compromising tissue perfusion. Sepsis syndrome also generates myocardial depressant substances [9] that interfere directly with cardiac contractility, thereby contributing to hypotension. However, ARF in the course of sepsis may not be solely due to systemic or renal hemodynamic changes, since humural (hormones, vasoactive mediators) and cellular (activation of leukocytes) reactions may also have an adverse effect on renal function [10].

The Severe Cardiorenal Syndrome

Thesis

Full-text available

Feb 2011

Lennart Bongartz

http://dspace.library.uu.nl/handle/1874/197549 ISBN 978-90-8891-240-5 Source Universiteit Utrecht In this thesis we investigated the interactions between heart and kidneys in disease in a longitudinal and integrative fashion. We developed two different rat models of the Severe Cardiorenal Syndrome and studied the effects of different interventions on progression of cardiorenal failure and on structural and functional outcome. In Part I we propose the Cardiorenal Connection (CRC) as a pathophysiological model in which the cardiorenal connectors interact and synergize to cause accelerated cardiovascular damage in the SCRS. The connectors are: (1) an imbalance between nitric oxide (NO) and reactive oxygen species (ROS), (2) activation of the sympathetic nervous system (SNS) (3) activation of the renin-angiotensin system (RAS), and (4) induction of inflammation. In Part II we describe the development of a model of combined chronic kidney disease (CKD) and heart failure (HF), and found evidence of bi-directional organ damage and the effect of interventions targeted at the CRC. We found that pre-existent CKD aggravated cardiac dilatation after MI that was associated with worsened cardiac diastolic and systolic function, and mortality. Conversely, the ensuing HF exacerbated glomerular damage in CKD rats, which was not associated with worsening of creatinine clearance or proteinuria. Blockade of all cardiorenal connectors with angiotensin receptor blockade and beta-blockade, systemic supplementation of NO, and anti-oxidant and anti-inflammatory therapy had significant beneficial effects on cardiorenal outcome: cardiac systolic function was preserved, glomerular damage was ameliorated, and tubulointerstitial damage was almost completely reversed. Blockade of 3 or 1 cardiorenal connectors resulted in a similar upholding of systolic function but had less effect on renal injury. We further described increased cardiac hepcidin expression in rats with SNX or CL, as well as in the combination. In contrast, liver hepcidin expression was not affected by both single insults but down-regulated in combined SNX and CL. Part III describes investigations into the role of nitric oxide (NO) in cardiac dysfunction in CKD. Low dose NO synthase (NOS) inhibition during CKD induced worsened proteinuria, severe cardiac dysfunction and reduced systemic NO production as compared to rats with CKD alone and controls treated with a similar dose of NOS inhibition. Furthermore, the increased protein excretion, the cardiac dysfunction and the low NO production after cessation of NOS inhibition. The mild hemodynamic effects of low dose NOS inhibition observed in controls were fully reversible. The findings of the previous study strongly suggested a causal link between NO availability and cardiac function. We investigated the effect of systemic NO supplementation with the tolerance-free NO donor molsidomine (MOLS) as a rescue therapy. MOLS significantly improved diastolic and systolic heart function, with mild effects on cardiac loading conditions and LVH, and no effects on cardiac fibrosis. Creatinine clearance and tubulo-interstitial injury improved, but no effect was seen on proteinuria. Expression of nNOS was increased compared to controls in this model of the SCRS. We assessed the effect of selective nNOS blockade in baseline and under beta-adrenergic stimulation and found that nNOS derived NO supports diastolic relaxation in CRS rats, but does not modulate the impaired beta-adrenergic response

Effects of Hypoxia on Inducible Nitric Oxide Synthase (iNOS) in Renal Mesangial Cells

Chapter

Jan 1995

The effects of hypoxia on the molecular biology and enzyme activity of nitric oxide synthase (NOS) have, until recently, been unclear due to problems measuring nitric oxide (NO), failure to examine the entire NOS pathway, and variable definitions of hypoxia. This chapter describes recent advances in our understanding of the effects of hypoxia on the inducible isoform of nitric oxide synthase (iNOS). The renal mesangial cell was chosen as a model in which to study the effects of hypoxia on iNOS because these cells make NO in sepsis, lack the constitutive form of NOS (cNOS) and, when primed with lipopolysaccharide (LPS), are prolific generators of NO. The importance of examining the iNOS pathway at multiple levels, from induction of messenger ribonucleic acid (mRNA) and iNOS activity to the postsynthetic fate of NO and activation of molecular targets, is explained.

NO and The Renin System

Chapter

Jan 1997

The renin—angiotensin—aldosterone cascade plays an important role in the blood pressure, electrolyte, and fluid homeostasis of the organism. The activity of the renin—angiotensin system in the circulation is mainly dependent on the activity of the protease renin, which is considered the key regulator of the system. Renin found in the circulation comes predominantly from the kidneys, where renin is produced primarily by the so-called juxtaglomerular epitheloid (JGE) cells. These cells are located in the media layer of the afferent arterioles adjacent to the vascular poles of the glomeruli [12]. JGE cells develop from vascular smooth cells by a reversible metaplastic transformation [12]. This differentiation is associated by a marked change of cell morphology in a way that numerous granular (renin storage) vesicles of various size and shape appear while the number of myofilaments disappear [1]. The morphologic appearance of the cells becomes more epitheloid rather than smooth muscle cell-like. Which intracellular events trigger and control the shift of smooth muscle cells into JGE cells and back is not yet known. The JGE cells are directly neighbored to four cell types: smooth muscle cells of the afferent arterioles, endothelial cells covering the interior of the afferent arterioles, mesangial cells of the glomeruli, and the macula densa cells. It is conceivable, therefore, that the functions of JGE cells, namely renin synthesis and renin secretion, are essentially modulated by these neighboring cells. In fact, it is known that the macula densa cells exert influence on JGE cells by a yet undefined “macula densa signal” which acts inhibitorily on renin secretion and renin synthesis [3].

Role of NO in the Function of the Juxtaglomerular Apparatus

Chapter

Jan 1997

Juxtaglomerular apparatus (JGA) is the anatomical term for a conglomeration of specialized cells positioned at the vascular pole of the renal glomerulus. The constituents of this cell complex are epithelial, interstitial, and modified smooth muscle cells. The epithelial cells of the JGA are located at the distal end of the thick ascending limbs, a part of the nephron that always returns to the vascular pole of its parent glomerulus. The tubular cells in this contact area, called the macula densa (MD) cells, are cytologically distinct from the surrounding thick ascending limb cells. Underlying the MD cell plaque and filling the space between it and the arterioles is a cushionlike complex of specialized interstitial cells, called the extraglomerular mesangium (EGM). In their fine structure, EGM cells are similar to intraglomerular mesangial cells. EGM cells are coupled by an extensive network of gap junctions with each other. They are also coupled with vascular smooth muscle cells in the afferent arteriole and with the renin-containing granular cells in the media of the arteriolar wall. This anatomical arrangement is the probable route for a communication pathway along which changes in tubular fluid composition in the tubular lumen at the macula densa initiate successive alterations in the functional state of MD cells, EGM cells, and, finally, vascular smooth muscle and granular cells.

Nitric Oxide and Hypertension: Physiology and Pathophysiology

Chapter

Jan 1997

The field of nitric oxide (NO) research has progressed rapidly and yielded many unexpected insights into cardiovascular control. In 1980 the phenomenon of endothelium-dependent relaxation and the existence of the endothelium-derived relaxing factor (EDRF) were described [1]. Seven years later EDRF was identified as an inorganic gas, NO [2]. Now it is clear that neurones, smooth muscle cells, cardiac myocytes, white cells and platelets, as well as endothelial cells all have the capacity to affect cardiovascular behaviour through generation of NO. Here we discuss the role of NO in the maintenance of normal blood pressure and flow, and describe the significance of the changes that occur in experimental and clinical hypertension. We have reviewed the role of NO in hypotension elsewhere [3].

Lifestyle Intervention

Chapter

Dec 2015

Lifestyle changes are a more “natural” way toward therapeutic goals and should be an integral component of halting or even reversing early vascular aging (EVA). However, the vague and rather immense meaning of the term “lifestyle” includes many distinct elements of everyday life. Examples of lifestyle modification are numerous, and include, apart from what we eat and drink, physical activity, weight reduction, smoking, and stress. The aim of this chapter is to scrutinize the impact of various lifestyle factors on arterial structure and function; to this end, both cross-sectional as well as interventional studies are presented. In most of them, indices of arterial stiffness and wave reflections have been used as a proxy for EVA.

Nitrite and Nitrate Plasma Levels, as Markers for Nitric Oxide Synthesis, in Thrombotic Thrombocytopenic Purpura (TTP): A Case-Control Study

Article

Jan 1996

The enhanced platelet aggregation and thrombosis occurring in TTP is probably due to an unbalance between agents insulting endothelial integrity and natural antithrombotic factors, such as NO. Using a sensitive and specific HPLC assay, we tested the hypothesis of NO involvement in TTP, comparing NO production, as the stable end-products nitrites and nitrates, in the plasma of 29 TTP patients and of 29 healthy subjects matched for sex and age. Average nitrate titer was 25.868 μM/L in the TTP group vs 24.234 μM/L in the control group (p = n.s.), while nitrite were undetectable in both groups. Moreover, nitrate titers did not correlate with hemoglobin value, platelet count, LDH values, or with Rose and Elder's severity score. In conclusion, even though the enhanced platelet aggregation observed in TTP could be due to reduced natural antithrombotic substances, NO involvement in the pathogenesis of TTP appears unlikely.

Tubuloglomerular Feedback and Macula Densa-Derived NO

Chapter

Jan 1997

Tubuloglomerular feedback (TGF) is an intrarenal regulatory mechanism that stabilizes the glomerular filtration rate (GFR) and distal delivery of NaC1 and fluid during periods in which homeostasis is challenged, such as changes in systemic blood pressure. The system acts at the single-nephron level primarily by increasing tone at the afferent arteriole, thus reducing glomerular capillary pressure (PGC), in response to increased delivery of NaC1 and fluid to the macula densa segment of the nephron. The macula densa is the site of signal transduction, where changes in solute delivery are sensed and initiation or release of vasoactive mediators occurs. TGF may also maintain homeostasis through regulation of sodium excretion, because increased delivery of sodium chloride to the macula densa activates TGF and decreases single-nephron GFR, thus adjusting the rate of sodium excretion.

Pharmacologic and Environmental Factors: Coffee, Smoking, and Sodium

Article

Feb 2015

Given the prognostic role of arterial stiffness and central hemodynamics [1–4], a large body of research has focused on the recognition of lifestyle interventions that may either worsen arterial function, and thus, they should be prohibited or at least discouraged, or exert favorable effects, and, consequently, they should be encouraged.

Diuretic activity of carob ( Ceratonia silique L.) Honey: comparison with furosemide

Article

Full-text available

Jul 2015

Endothelin-B (ETB) receptors and blood pressure in experimental hypertension in rats

Article

Jul 2005

Endothelin-B receptors (ETBR), located mainly on endothelial cells, produce vasodilator effects by releasing either nitric oxide (NO) and/or prostacyclin (PGI2). Several reports have suggested impaired endothelial NO production in Dahl salt-sensitive (DS) rats. This impaired NO production complicates the understanding of the ETBR response in this salt-sensitive model. The aim of the study reported here was to determine the physiological role of the ETBR and the main pathway through which the receptors exhibit their effects in salt-sensitive hypertension, using DS rats. Hypertension was induced in the rats over a 4-week period by giving a 2% NaCl solution. The animals were divided into three groups. BQ-788 (a selective ETBR antagonist) was given to the first group, to determine whether ETBR played a role in blood pressure (BP) of hypertensive rats. L-NAME (NO synthase inhibitor) was given to the second group to determine the effects of NO on the BP of hypertensive rats. The third group received L-NAME + BQ-788, to determine the specific role of NO response to ETBR activation. These drugs were administered intravenously and aortic BP recorded before and after the intervention. Administration of BQ-788 to rats pre-treated with L-NAME (group 3) showed a significant increase in all BP parameters measured. Similar diastolic BP results in the L-NAME and L-NAME + BQ-788 groups were observed. Since administration of the ETBR antagonist in the rats pre-treated with L-NAME did not produce an intensified response compared to L-NAME alone, our results suggested that NO is probably the dominant factor in the ETBR response in this salt-sensitive hypertension model.

Physiology of the Developing Kidney: Sodium and Water Homeostasis and Its Disorders

Chapter

Feb 2015

Salt and water are the stuff of life [1, 2]. The ancient and the modern voices have been invoked in the past to demonstrate that human beings intuitively appreciate the critical role played by sodium and water balance for the integrity of the plasma compartment and for continued existence on land. The third time around, I turn to a towering contemporary figure of our age as inspiration for this chapter. The material will review the physiological mechanisms involved in the control of sodium and water homeostasis. This knowledge will provide a basis for the analysis of the diseases that arise when these systems malfunction and a guide to the optimal therapy of conditions associated with excessive or deficient total body sodium and water.

Sodium and Water

Chapter

Jan 2009

Howard Trachtman

There must be something about the topic of sodium and water homeostasis that reaches deep within the human psyche and prompts authors to wax poetic in search of literary aphorisms (1, 2). In the past, the author looked to the ancients to demonstrate that human beings probably have an intuitive sense of the critical role played by salt balance and the integrity of the plasma compartment for the maintenance of life in terrestrial species. For the second time, the author turns to a contemporary voice for inspiration in this chapter that reviews the physiological mechanisms involved in the control of sodium and water homeostasis. Using this knowledge as a basis, there will be an analysis of the common diseases that arise when these systems malfunction and a discussion of the optimal therapy for these conditions.

Cardiovascular Effects of Dietary Salts and Isosorbide-5-Mononitrate in Spontaneously Hypertensive Rats

Article

Jan 1998

Timo Vaskonen, Eero Mervaala, Tertt

effects of dietary salts and isosorbide-5-mononitrate in spontaneously hypertensive rats. Blood Pressure 1998; 7: 184‐192. The influence of isosorbide-5-mononitrate (IS-5-MN) on the cardiovascular effects of high dietary salt intake (NaCl, 6.6% of dry weight of food) and that of a potassium, magnesium and l-lysine-enriched salt alternative (Pansalt 10.5%, producing a 6.6% content of NaCl) was studied in spontaneously hypertensive rats in an 8-week experiment. Common salt produced a marked rise in blood pressure and induced cardiac and renal hypertrophy, while the salt alternative, although containing the same amount of NaCl, neither increased blood pressure nor caused any significant cardiac hypertrophy. IS-5-MN treatment at a daily dose of approximately 60‐ 70 mg/kg (mixed with food) attenuated the rise in blood pressure induced by common salt, but did not prevent the cardiac or renal hypertrophy. IS-5-MN did not offer any additional benefit to the use of the salt alternative diet alone in treatment of high blood pressure. Mesenteric arterial responses in vitro were examined at the end of the study. IS-5-MN treatment during the moderately low-salt (NaCl 0.7%) control diet tended to decrease the contractile response to noradrenaline and increase the relaxation to acetylcholine. Common salt, but not the salt alternative, induced a 50% increase in the 24-h urinary excretion of cyclic GMP. Both salt supplements induced an 8‐ 9-fold increase in the excretion of calcium, and about a 2-fold increase in the excretion of phosphorus. Common salt also increased the excretion of magnesium by 50%. IS-5-MN treatment had no significant effect on the excretion of the mineral elements. Our findings show that increased intake of potassium and magnesium reduces the harmful effects of common salt. Pressure-independent mechanisms are involved in salt-induced left ventricular and renal hypertrophy, since they remained unaffected despite the prevention of the salt-induced rise in blood pressure by IS-5-MN treatment. Key words: blood pressure, isosorbide-5-mononitrate, left ventricular hypertrophy, magnesium, potassium, renal hypertrophy, SHR, sodium.

Role of nitric oxide and prostacyclin in the control of renal perfusion in experimental cirrhosis*1, *2

Article

Sep 1995

Josefa Ros

Nitric oxide (NO) and prostacyclin (PGI2) are two important modulators of renal function under normal conditions; however, little is known on their contributory role in cirrhosis with ascites. In this study, mean arterial pressure, renal hemodynamics, and sodium excretion were measured in 15 rats with cirrhosis and ascites and 16 control rats. Animals were studied in normal conditions, after inhibiting the synthesis of NO (Nω-nitro-l-arginine, 50 μg · kg−1· min−1) or prostaglandins (lysine acetylsalicylate, 15 mg · kg−1 · min−1) and following the concomitant inhibition of both systems. Cirrhotic rats showed increased systemic pressure sensitivity and blunted renal vasoconstrictor response to nitric oxide inhibition as compared with control rats. As a consequence, the glomerular filtration rate increased in cirrhotic rats but not in control rats. In both groups of animals, NO inhibition was associated with significant increased urinary sodium and fractional sodium excretion. The only significant effect observed after prostaglandin biosynthesis inhibition was a decrease in renal plasma flow in cirrhotic rats. The concomitant inhibition of both systems reduced renal plasma flow and did not change glomerular filtration rate, with no differences between control and cirrhotic rats. Prostaglandin inhibition did not prevent the natriuretic effect of the NO inhibitor in both groups of animals. These results indicate that in experimental cirrhosis both NO and PGI2 play an important role in the maintenance of renal perfusion within normal limits.

Morrison 2007 High fat diet Zucker

Data

Full-text available

Jan 2015

Impairment of Endothelial Function in Salt-Sensitive Hypertension in Humans

Article

Oct 1997

Aya Miyoshi

In this study, we evaluated the relationship between the endothelium-dependent vasodilation and salt sensitivity in patients with essential hypertension. Fifteen untreated hypertensive male patients (age, 29 to 54 years) were sodium restricted (5 g/day) for 1 week, and placed on a high salt diet (20 g/day) the second week. At the end of each period, measurements of forearm vascular responses to drugs (acetylcholine, 3 to 24 μg/min; sodium nitroprusside, 0.15 to 1.2 μg/min; norepinephrine, 0.15 to 1.2 μg/min; and G-monomethyl-L-arginine [L-NMMA], 1 to 8 μmol/min) were obtained by using strain-gauge venous plethysmography. Subjects were divided into two groups according to the blood pressure response to sodium loading: salt-sensitive hypertensive group (24-h mean increase of arterial pressure ≥10%; n = 6) and salt-resistant group (<10%; n = 9). The two groups showed no significant difference in clinical data or mean arterial pressure during low salt intake. The dose-dependent vasodilation induced by acetylcholine was significantly reduced (P < .05) in the salt-sensitive hypertensive patients v the salt-resistant patients regardless of sodium loading. There were no differences between the two groups in response to sodium nitroprusside, norepinephrine, or L-NMMA. These results indicate that vasodilation to acetylcholine is reduced in salt-sensitive hypertensive patients even on restricted sodium diets. This may contribute to blood pressure elevation when sodium intake is increased. Am J Hypertens 1997;10:1083–1090 © 1997 American Journal of Hypertension, Ltd.

Beeinflussung der renalen und systemischen Hämodynamik durch Infusion von Tetrahydrobiopterin (BH 4 ) bei gesunden Probanden

Article

The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholin

Article

Full-text available

Nov 1980
NATURE

Evidence for cytokine-inducible nitric oxide synthesis from L-arginine in patients receiving interleukin-2 therapy

Article

Full-text available

Apr 1992

An interferon-gamma, tumor necrosis factor, and interleukin-1-inducible, high-output pathway synthesizing nitric oxide (NO) from L-arginine was recently identified in rodents. High-dose interleukin-2 (IL-2) therapy is known to induce the same cytokines in patients with advanced cancer. Therefore, we examined renal cell carcinoma (RCC; n = 5) and malignant melanoma (MM; n = 7) patients for evidence of cytokine-inducible NO synthesis. Activity of this pathway was evaluated by measuring serum and urine nitrate (the stable degradation product of NO) during IL-2 therapy. IL-2 administration caused a striking increase in NO generation as reflected by serum nitrate levels (10- and 8-fold increase [P less than 0.001, P less than 0.003] for RCC and MM patients, respectively) and 24-h urinary nitrate excretion (6.5- and 9-fold increase [both P less than 0.001] for RCC and MM patients, respectively). IL-2-induced renal dysfunction made only a minor contribution to increased serum nitrate levels. Metabolic tracer studies using L-[guanidino-15N2]arginine demonstrated that the increased nitrate production was derived from a terminal guanidino nitrogen atom of L-arginine. Our results showing increased endogenous nitrate synthesis in patients receiving IL-2 demonstrate for the first time that a cytokine-inducible, high-output L-arginine/NO pathway exists in humans.

Nitric oxide and angiotensin II. Glomerular and tubular interaction in the rat

Article

Full-text available

May 1992

Nitric oxide (NO) has been proposed to modulate the renal response to protein as well as basal renal hemodynamics. We investigated whether NO and angiotensin II (AII) interact to control glomerular hemodynamics and absolute proximal tubular reabsorption (APR) during glycine infusion and in unstimulated conditions. In control rats, glycine increased single nephron GFR and plasma flow with no change in APR. The NO synthase blocker, NG-monomethyl L-arginine (LNMMA), abolished the vasodilatory response to glycine, possibly through activation of tubuloglomerular feedback due to a decrease in APR produced by LNMMA + glycine. Pretreatment with an AII receptor antagonist, DuP 753, normalized the response to glycine at both glomerular and tubular levels. In unstimulated conditions, LNMMA produced glomerular arteriolar vasoconstriction, decreased the glomerular ultrafiltration coefficient, and reduced single nephron GFR. These changes were associated with a striking decrease in APR. DuP 753 prevented both glomerular and tubular changes induced by LNMMA. In conclusion, NO represents a physiological antagonist of AII at both the glomerulus and tubule in both the basal state and during glycine infusion; and inhibition of NO apparently enhances or uncovers the inhibitory effect of AII on proximal reabsorption.

L-arginine abrogates salt-sensitive hypertension in Dahl/Rapp rats

Article

Full-text available

Dec 1991

This study examined the contribution of nitric oxide (NO) to the susceptibility or resistance to the hypertensive effects of high sodium chloride (8.0% NaCl) intake in young Dahl/Rapp salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats. Using NG-monomethyl-L-arginine (L-NMMA) as a probe for NO production in vivo, we found that increasing dietary sodium chloride increased NO activity in salt-resistant rats, but not in salt-sensitive rats. Exogenous L-arginine, the substrate for NO synthesis, decreased blood pressure to normotensive levels in salt-sensitive rats made hypertensive for 2 wk from 8.0% NaCl chow. D-arginine had no effect on blood pressure of these rats and L-arginine did not change blood pressure of salt-resistant rats. Intraperitoneal injections of L-arginine and its precursor, L-citrulline, and oral L-arginine, but not D-arginine, prevented the increase in blood pressure in salt-sensitive rats on the high salt chow over 2 wk of observation. In contrast, L-arginine did not alter the development of hypertension in spontaneously hypertensive rats. Mean urinary cGMP levels were higher in salt-sensitive rats on oral L-arginine than salt-sensitive rats on D-arginine. Infusion of L-NMMA acutely decreased, whereas intravenous L-arginine rapidly increased, urinary cGMP in both groups. L-arginine and L-citrulline increased production of NO and prevented salt-sensitive hypertension in Dahl/Rapp rats.

Interleukin 1 induces prolonged L-Arginine-dependent cyclic guanosine monophoshate and nitrite production in rat vascular smooth muscle cells

Article

Full-text available

Mar 1991

The cytokine interleukin 1 (IL-1) inhibits contractile responses in rat aorta by causing endothelium-independent and prolonged activation of soluble guanylate cyclase. The present study tested whether IL-1 activates guanylate cyclase by inducing prolonged production of nitric oxide in cultured rat aortic vascular smooth muscle cells (VSMC). IL-1 induced a marked time-dependent increase in cyclic guanosine monophosphate (cGMP) in VSMC which was significant at 6 h, and increased progressively for up to 36 h. This effect of IL-1 was abolished when protein synthesis was inhibited with cycloheximide or actinomycin D, suggesting that the effect of IL-1 involves new protein synthesis. IL-1-induced cGMP accumulation was inhibited by the soluble guanylate cyclase inhibitors, methylene blue, LY83583, and hemoglobin and by the L-arginine analogue NGmonomethyl-L-arginine (L-NMMA). The inhibitory effect of L-NMMA was reversed by a 10-fold excess of L-arginine, but not by D-arginine. Nitrite, an oxidation product of nitric oxide, accumulated in the media of VSMC incubated with IL-1 for 24 h in the presence of L-arginine, whereas both IL-1-induced cGMP accumulation and nitrite production were attenuated in VSMC incubated in L-arginine-deficient medium. In L-arginine-depleted VSMC, IL-1-induced cGMP accumulation was restored to control levels by a 15-min incubation with L-arginine. These results demonstrate that IL-1 activates guanylate cyclase in rat VSMC by inducing production of nitric oxide via a pathway dependent on extracellular L-arginine.

Bredt DS, Snyder SH.Isolation of nitric oxide synthase, a calmodulin-requiring enzyme. Proc Natl Acad Sci U S A 87: 682-685

Article

Full-text available

Feb 1990

Nitric oxide mediates vascular relaxing effects of endothelial cells, cytotoxic actions of macrophages and neutrophils, and influences of excitatory amino acids on cerebellar cyclic GMP. Its enzymatic formation from arginine by a soluble enzyme associated with stoichiometric production of citrulline requires NADPH and Ca2+. We show that nitric oxide synthetase activity requires calmodulin. Utilizing a 2',5'-ADP affinity column eluted with NADPH, we have purified nitric oxide synthetase 6000-fold to homogeneity from rat cerebellum. The purified enzyme migrates as a single 150-kDa band on SDS/PAGE, and the native enzyme appears to be a monomer.

Metabolic fate of L-arginine in relation to microbiostatic capacity of macrophages

Article

Full-text available

Feb 1990

L-arginine is required for the fungistatic action of murine macrophages in vitro. To further investigate this requirement, L-arginine metabolism by macrophages was measured under conditions where fungistasis either succeeded or failed. Macrophage fungistasis correlated with metabolism of L-arginine to citrulline, nitrite, and nitrate. The metabolic rate was dependent on extracellular L-arginine concentration, reaching a maximum of 67 nmol nitrite/h per mg protein. It accounted for one-third of arginine consumed by fungistatic macrophages. Equimolar amounts of citrulline and total nitrite plus nitrate accumulated in medium. This was consistent with the hypothesis that one of the equivalent guanidino nitrogens of L-arginine was oxidized to both nitrite and nitrate leaving L-citrulline as the amino acid reaction product. The analogue, NG-mono-methyl-L-arginine, selectively inhibited nitrogen oxidation and it was shown previously that it inhibited fungistatic capability. Resident macrophages were not fungistatic and their nitrogen oxidation was low. Once macrophages began producing nitrite/nitrate, protein synthesis was not required during the next 8 h for either fungistasis or nitrogen oxidation. Two-thirds of L-arginine consumption was due to macrophage arginase yielding L-ornithine and urea, which accumulated in medium. This activity was dissociated from macrophage fungistasis. Nitrogen oxidation metabolism by macrophages is linked to a mechanism that inhibits proliferation of fungi. This may involve synthesis of an intermediate compound(s) that has antimicrobial properties.

Analysis of nitrate, nitrite, and [15N] nitrate in biological fluids

Article

Full-text available

Nov 1982

A new automated system for the analysis of nitrate via reduction with a high-pressure cadmium column is described. Samples of urine, saliva, deproteinized plasma, gastric juice, and milk can be analyzed for nitrate, nitrite, or both with a lower limit of detection of 1.0 nmol NO3− or NO2−/ml. The system allows quantitative reduction of nitrate and automatically eliminates interference from other compounds normally present in urine and other biological fluids. Analysis rate is 30 samples per hour, with preparation for most samples limited to simple dilution with distilled water. The application of gas chromatography/mass spectrometry for the analysis of 15NO3− in urine after derivatization to 15NO2-benzene is also described.

Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide

Article

Dec 1987

The objective of this study was to determine whether nitric oxide (NO) is responsible for the vascular smooth muscle relaxation elicited by endothelium-derived relaxing factor (EDRF). EDRF is an unstable humoral substance released from artery and vein that mediates the action of endothelium-dependent vasodilators. NO is an unstable endothelium-independent vasodilator that is released from vasodilator drugs such as nitroprusside and glyceryl trinitrate. We have repeatedly observed that the actions of NO on vascular smooth muscle closely resemble those of EDRF. In the present study the vascular effects of EDRF released from perfused bovine intrapulmonary artery and vein were compared with the effects of NO delivered by superfusion over endothelium-denuded arterial and venous strips arranged in a cascade. EDRF was indistinguishable from NO in that both were labile (t1/2 = 3-5 sec), inactivated by pyrogallol or superoxide anion, stabilized by superoxide dismutase, and inhibited by oxyhemoglobin or potassium. Both EDRF and NO produced comparable increases in cyclic GMP accumulation in artery and vein, and this cyclic GMP accumulation was inhibited by pyrogallol, oxyhemoglobin, potassium, and methylene blue. EDRF was identified chemically as NO, or a labile nitroso species, by two procedures. First, like NO, EDRF released from freshly isolated aortic endothelial cells reacted with hemoglobin to yield nitrosylhemoglobin. Second, EDRF and NO each similarly promoted the diazotization of sulfanilic acid and yielded the same reaction product after coupling with N-(1-naphthyl)-ethylenediamine. Thus, EDRF released from artery and vein possesses identical biological and chemical properties as NO.

Vascular endothelial cells synthesize nitric oxide from L-arginine

Article

Jul 1988

Nitric oxide (NO) released by vascular endothelial cells accounts for the relaxation of strips of vascular tissue1 and for the inhibition of platelet aggregation2 and platelet adhesion3 attributed to endothelium-derived relaxing factor4. We now demonstrate that NO can be synthesized from L-arginine by porcine aortic endothelial cells in culture. Nitric oxide was detected by bioassay5, chemiluminescence1 or by mass spectrometry. Release of NO from the endothelial cells induced by bradykinin and the calcium ionophore A23187 was reversibly enhanced by infusions of L-arginine and L-citrulline, but not D-arginine or other close structural analogues. Mass spectrometry studies using 15N-labelled L-arginine indicated that this enhancement was due to the formation of NO from the terminal guanidino nitrogen atom(s) of L-arginine. The strict substrate specificity of this reaction suggests that L-arginine is the precursor for NO synthesis in vascular endothelial cells.

Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme

Article

Jan 1990

The endothelium. Target and promoter of hypertension?

Article

May 1990

Thomas F Luscher

Macromolecule Transport across Glomerular Capillaries: Application of Pore Theory

Article

Oct 1979

Measurements of transport rates of various high-molecular-weight solutes across capillaries have contributed significantly to our understanding of the functional properties of both renal and extrarenal microcirculatory systems [1–7]. In addition to serum albumin and other plasma proteins, nonprotein polymers such as dextran and polyvinylpyrrolidone (PVP) also have been used successfully as transport probes. Complementing these quantitative measurements of macromolecular transport are the more qualitative insights into permeation pathways gained from studies with macro-molecules as ultrastructural tracers [6, 8, 9]. As a result of these investigations, it has become apparent that several factors influence the transcapillary movement of macromolecules, including molecular size, molecular charge, and perhaps even “shape”. In addition, transport rates are known also to be influenced by plasma flow rate and other hemodynamic variables. In an effort to better understand how these various factors combine to govern the transport of macromolecules, several theoretical descriptions of transcapillary exchange have been developed. Much of this work has been based on hydrodynamic models of solute transport through pores, first applied to capillaries by Pappenheimer [4] and Pappenheimer, Renkin, and Borrero [10]. This review will summarize the current status of the pore model, with emphasis on its application to the study of macromolecule transport across glomerular capillaries.

Mechammi of angioteisn II-induced proteinuria In the rat

Article

Aug 1977
Am J Physiol

To investigate the mechanism(s) of angiotensin II-induced proteinuria, polydisperse [3H]dextran (D) (radius = 18-42 A) was infused into seven Munich-Wistar rats before and during intravenous infusion of angiotensin II (AII), 0.35 microgram/kg per min. During AII infusion, UprotV rose approximately twofold, and the fractional clearances of D [(U/P)D/(U/P)In] increased significantly for dextrans with radii greater than 22 A. Single nephron filtration fraction increased, due to a measured rise in the glomerular transcapillary hydraulic pressure difference from 34 to 43 mmHg. Near constancy of single nephron glomerular filtration rate resulted, however, from the offsetting effect of a decrease in glomerular plasma flow rate from 83 to 60 nl/min. These measured hemodynamic changes were found, by the use of pore theory, to account to a large extent for the measured increases in (U/P)D/(U/P)In. In seven other rats, fractional clearances of polyanionic dex-ran sulfate (a more reliable marker of albumin filtration than D) were also found to increase significantly with AII, suggesting that the proteinuria induced by AII can be explained, in large part, by hemodynamic factors.

Effects of some transcapillary fluid exchange in renal cortex

Article

May 1976
Am J Physiol

In 23 Munich-Wistar rats with surface glomeruli, the determinants of glomerular ultrafiltration and peritubular capillary uptake of proximal reabsorbate were studied before and during intra-arterial infusions of mildly vasodepressor doses of prostaglandin E1,acetylcholine, and bradykinin. For each drug single-nephron glomerular filtration rate remained unchanged from normal hydropenic values while glomerular plasma flow rate increased, resulting in declines in single-nephron filtration fraction (SNFF). Mean glomerular transcapillary hydraulic pressure difference (delta P) increased or remained unchanged on average. Declines in SNFF were accompanied by reductions in efferent arteriolar oncotic pressure (piE). Filtration pressure equilibrium, equality between pi E and delta P, obtained before but not during drug infusions. In the latter situation values for the glomerular capillary ultrafiltration coefficient were calculated and found to be significantly reduced from published control values. Despite marked falls in pi E during drug infusion, absolute proximal reabsorption was not reduced significantly, due, it is suggested, to the opposing effects of increases in efferent arteriolar plasma flow and interstitial hydraulic pressure.

Pressure natriuresis in rats during blockade of the l-Arginine/Nitric Oxide pathway

Article

May 1992

The natriuretic response was studied in anesthetized rats during the intravenous infusion of L-arginine analogues to inhibit the production of endothelium-derived nitric oxide. In an initial experimental series, rats were administered saline vehicle or vehicle containing 300 mumol/kg body wt N omega-monomethyl-L-arginine, N omega-nitro-L-arginine methyl ester, N omega-monomethyl-D-arginine, or L-arginine. Infusion of the competitive inhibitors N omega-monomethyl-L-arginine and N omega-nitro-L-arginine methyl ester significantly increased mean arterial pressure to 155 +/- 3 and 145 +/- 5 mm Hg, respectively, compared with a mean arterial pressure of 118 +/- 3 mm Hg determined in the vehicle control group. Sodium excretion averaged 3.27 +/- 1.08 and 2.52 +/- 0.78 mu eq/min in the N omega-monomethyl-L-arginine- and N omega-nitro-L-arginine methyl ester-treated rats, respectively, and each was significantly higher than the basal sodium excretion of 0.20 +/- 0.05 mu eq/min in the vehicle-treated control animals. Plasma renin activity was significantly lower in the N omega-monomethyl-L-arginine- and N omega-nitro-L-arginine methyl ester-treated groups than in the vehicle-treated group. Neither L-arginine nor N omega-monomethyl-D-arginine administration significantly altered any of the measured variables compared with vehicle alone. In a second experimental series, an adjustable snare was placed around the suprarenal aorta for the purpose of controlling renal perfusion pressure independently of increases in the systemic mean arterial pressure initiated by infusion of N omega-nitro-L-arginine methyl ester (75 mumol/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Endogenously synthesized nitric oxide prevents endotoxin-induced glomerular thrombosis

Article

Dec 1992

Escherichia coli endotoxin (LPS) can induce the clinical syndrome of septic shock and renal cortical necrosis and can stimulate nitric oxide (NO) production from macrophages, vascular smooth muscle, and glomerular mesangial cells in vitro. NO is an endogenous vasodilator, which also inhibits platelet aggregation and adhesion. We therefore sought to determine whether LPS would stimulate NO production in vivo and, if so, whether this NO would modulate endotoxin-induced glomerular thrombosis. The stable NO end-products, NO2 and NO3, were measured in serum and urine collections from rats during baseline and after injection of LPS, with or without substances that modulate NO synthesis. The urinary excretion of NO2/NO3 was 1,964 +/- 311 nm/8 h during the baseline and increased to 6,833 +/- 776 nm/8 h after a single intraperitoneal injection of 0.1 mg/kg LPS (P < 0.05). The serum concentration of NO2/NO3 also significantly increased after LPS injection. Both the urine and serum stimulation was significantly prevented by the NO synthesis inhibitor, Nw-nitro-L-arginine methyl ester (L-NAME). L-Arginine, given with LPS+L-NAME significantly restored the NO2/NO3 levels in the urine. Ex vivo incubation of tissues from rats treated with LPS demonstrated NO production by the aorta, whole kidney, and glomeruli, but not cortical tubules. Histological examination of kidneys from rats given either LPS or L-NAME alone revealed that 2 and 4.5% of the glomeruli contained capillary thrombosis, respectively. In contrast, rats given LPS+L-NAME developed thrombosis in 55% of glomeruli (P < 0.001), which was significantly prevented when L-arginine was given concomitantly. We conclude that LPS stimulates endogenous production of NO in vivo and that this NO is critical in preventing LPS-induced renal thrombosis.

Role of nitric oxide in mediating renal response to volume expansion

Article

Jul 1992

The objective of the present study was to determine the role of endothelium-derived nitric oxide in mediating the renal response to extracellular volume expansion with isotonic saline (5% body weight). In anesthetized dogs (n = 7) and before volume expansion, nitric oxide synthesis was inhibited in the right kidney by continuous intrarenal infusion of NG-nitro-L-arginine-methyl ester (1 microgram/kg/min). Arterial pressure and renal hemodynamics of both kidneys did not change significantly either during nitric oxide synthesis inhibition or during 5% volume expansion. However, in response to extracellular volume expansion, increases in natriuresis, diuresis, and fractional excretion of lithium (an index of proximal sodium reabsorption) were inhibited in the right kidney by 27%, 28%, and 41%, respectively, when compared with the contralateral kidney. Increases of renal interstitial hydrostatic pressure during 5% volume expansion were not statistically different between both kidneys. In another group of dogs (n = 4), the administration of L-arginine (0.5 mg/kg/min) into the right renal artery prevented the renal effects induced by the nitric oxide synthesis inhibitor during volume expansion. The findings in this study suggest that nitric oxide production plays an important role in regulating the renal response to extracellular volume expansion. The proximal tubule seems to be involved in the reduced renal excretory response to volume expansion during nitric oxide synthesis inhibition.

Synthesis and action of nitric oxide in rat glomerular mesangial cells

Article

Nov 1991
Am J Physiol

Macrophages and certain tumor cell lines can be induced to synthesize nitric oxide (NO) from L-arginine after stimulation with lipopolysaccharide (LPS) or cytokines. In the present study, we have found that culture medium collected after 24 h from unstimulated rat mesangial cells (MC) contains 6.3 +/- 1.2 microM of NO3-/NO2- (the degradation products of NO). These levels were significantly increased when MC were incubated with LPS (10 micrograms/ml) for 24 h (23.9 +/- 4.1, P less than 0.05). The specific inhibitor of NO synthesis, NG-monomethyl-L-arginine (L-NMMA) completely inhibited LPS-stimulated production of NO3-/NO2-, confirming that the NO3-/NO2- was derived from NO within the MC. Recent studies suggest that endothelium-derived relaxing factor (EDRF) produced by vascular endothelium is also NO, and we have previously shown that both EDRF and NO stimulate increases in MC guanosine 3',5'-cyclic monophosphate (cGMP). Thus we sought to determine whether NO synthesized by the MC could affect cGMP levels within the same cells. After 24-h incubation with LPS (10 micrograms/ml), intracellular cGMP level within the MC was 706.3 +/- 197 (SE) compared with 40.5 +/- 7 fmol/micrograms protein in control MC incubated in media alone (P less than 0.01). The changes in cGMP in response to LPS were inhibited by greater than 90% by L-NMMA. Similar to LPS, incubation of MC with the cytokine gamma-interferon also increased NO3-/NO2- in the culture media and increased cGMP levels within MC. The induction of NO synthesis within MC and the concomitant stimulation of MC cGMP may be important in the modulation of the effects of endotoxemia, as well as inflammation, within the glomerulus.

Suppression of blood flow autoregulation during nitric oxide blockade in canine kidney

Article

Feb 1992
Am J Physiol

We examined the autoregulation of renal blood flow (RBF) and renal function in anesthetized dogs during nitro-L-arginine (NLA)-induced blockade of endothelium-derived nitric oxide (EDNO). Intrarenal infusion of NLA (50 micrograms.kg-1.min-1) increased systemic arterial pressure (AP) and renal vascular resistance (RVR). RBF decreased by 27 +/- 3%, but glomerular filtration rate remained unchanged. There were reductions in urine flow (24 +/- 5%), urinary sodium excretion (42 +/- 10%), and fractional excretion of sodium (40 +/- 11%). The vasodilatory responses to intrarenal injections of ATP (1, 5, 10 microM) were reversed, whereas such responses to doses (10, 50, 100 ng) of acetylcholine (ACh) were attenuated during NLA infusion. Indomethacin (5 mg/kg iv) treatment further reduced but did not completely abolish ACh-induced vasodilation, suggesting that factor(s) other than EDNO and prostaglandins may also mediate ACh-induced vasodilation in the kidney. Although there was a suppression of the plateau of the AP-RBF relationship with a rightward shift in the slope of the linear portion of the curve during EDNO blockade, the normal autoregulatory pattern remained intact. Similar responses were seen in dogs treated with the angiotensin-converting enzyme inhibitor, MK-422. These data indicate that EDNO contributes to the normally low renal vascular tone by influencing an autoregulation-independent component of RVR. However, the basic capability to adjust RVR (autoregulation-responsive component) in response to changes in AP is essentially autonomous from EDNO activity.

Effects of NG-nitro-L-arginine methyl ester on renal function and blood pressure

Article

Jan 1992
Am J Physiol

The dose-dependent effects of intravenous infusions of nitric oxide (NO) synthesis inhibitor, NG-nitro-L-arginine methyl ester (L-NAME; 0.1, 1, 10, and 50 micrograms.kg-1.min-1), were studied in anesthetized rats to determine whether the inhibitory actions of L-NAME are manifested primarily in alterations of renal function or whether they are the consequences of the increase in systemic blood pressure. Mean arterial pressure (MAP) was not altered by the intravenous L-NAME infusions of 0.1 and 1.0 microgram.kg-1.min-1. However, 0.1 microgram.kg-1.min-1 L-NAME induced a 30% decrease in urine flow rate (UV). The administration of 1.0 microgram.kg-1.min-1 L-NAME, in addition to decreasing UV, also decreased urinary sodium excretion (UNaV) and renal plasma flow (RPF). The intravenous L-NAME infusions of 10.0 and 50.0 microgram.kg-1.min-1 intravenous L-NAME infusions of 10.0 and 50.0 microgram.kg-1.min-1 produced significant increases in MAP that reversed the initial fall in UV and UNaV, despite decreasing RPF and glomerular filtration rate (GFR). The administration of L-arginine alone (10 micrograms.kg-1.min-1) did not modify any of the parameters measured, but it effectively prevented all the hemodynamic and renal changes induced by the infusion of 50 micrograms.kg-1.min-1 L-NAME. These results suggest that the decrease in nitric oxide production induced by the intravenous infusion of L-NAME affects renal excretion of sodium and water in the absence of any significant change in blood pressure. At larger doses, L-NAME also produces hypertension that overrides the initial antinatriuretic effect.

Effects of nitric oxide inhibition on rat glomerular microcirculation

Article

Sep 1991
Am J Physiol

Endothelium-derived relaxing factor (EDRF), recently identified as nitric oxide (NO), has been shown to be released by glomerular endothelial cells and might influence the glomerular microcirculation. To examine this hypothesis, we studied in rats the renal effect of acute administration of NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of NO synthesis. Adult male Munich-Wistar rats were studied before and after intravenous administration of either pure saline or a bolus injection of L-NMMA (20 mg) followed by a continuous infusion of the inhibitor (0.4 mg/min). Although saline alone had no effect on systemic or glomerular hemodynamics, L-NMMA promoted marked systemic hypertension, glomerular arteriolar vasoconstriction, and glomerular hypoperfusion. Since efferent resistance was disproportionately increased, glomerular hydraulic pressure was also markedly elevated. The glomerular ultrafiltration coefficient (Kf) fell to 42% of control. Single-nephron glomerular filtration rate was unaffected. Striking polyuria was also observed. These findings suggest that EDRF exerts a basal relaxing effect on the glomerular microcirculation.

Nitric oxide: A potential mediator of amino acid-induced renal hyperemia and hyperfiltration

Article

Jul 1991

The role of nitric oxide in the modulation of systemic and renal hemodynamics was examined by using N omega-monomethyl-L-arginine (L-NMMA, 110 micrograms/kg/min), a competitive inhibitor of the conversion of L-arginine to nitric oxide. L-NMMA or saline vehicle (9.6 microL/min) was infused intravenously into anesthetized euvolemic Munich-Wistar rats. After 30 min, L-NMMA resulted in a uniform increase in mean arterial blood pressure (111 +/- 1 to 128 +/- 2 mmHg; P less than 0.05) and a modest reduction in renal plasma flow rate (4.4 +/- 0.2 to 4.2 +/- 0.1 mL/min; P less than 0.05), without change in glomerular filtration rate (1.16 +/- 0.03 to 1.15 +/- 0.03 mL/min); vehicle had no effect on these renal parameters. These rats were then subdivided to receive an intravenous infusion (37 microL/min) of either 10% glycine, 11.4% mixed amino acids, or equiosmolar dextrose. L-NMMA pretreatment markedly attenuated glycine-induced hyperfiltration (10 +/- 6 versus 33 +/- 5%, L-NMMA versus vehicle; P less than 0.05) and obliterated the renal hyperemic response (-7 +/- 6 versus 16 +/- 4%, L-NMMA versus vehicle; P less than 0.05). L-NMMA also caused modest blunting of the mixed amino acid-induced hyperfiltration (18 +/- 4 versus 30 +/- 4%, L-NMMA versus vehicle; P = 0.056) but failed to curtail the renal hyperemia (16 +/- 6 versus 20 +/- 4%). Dextrose had no effect on glomerular filtration rate or renal plasma flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of endothelium-derived relaxing factor in regulation of vascular tone and remodeling. Update on humoral regulation of vascular tone

Article

Jul 1991

In addition to preserving the permselectivity of the vascular wall and providing an antithrombogenic surface, the vascular endothelium contributes importantly to the regulation of vasomotor tone. Indeed, the endothelium participates in the conversion of angiotensin I to angiotensin II; the enzymatic inactivation of several plasma constituents such as bradykinin, norepinephrine, serotonin, and ADP; and the synthesis and release of vasodilator substances such as prostacyclin and the recently discovered endothelium-derived relaxing factor (EDRF). The diffusible EDRF released from the endothelium is nitric oxide or a substance closely related to it such as nitrosothiol. The endothelium also synthesizes and releases vasoconstrictive factors, including products derived from arachidonic acid metabolism and the recently discovered peptide endothelin. An increasing body of evidence from experimental and clinical studies indicates that EDRF and endothelium-derived contracting factors play an important role in vascular physiology and pathology. It has become apparent that the balance of these factors may be a major determinant of systemic and regional hemodynamics. Moreover, through generally opposite effects on growth-related vascular changes, contracting factors such as endothelin and relaxing factors such as EDRF also may be important determinants of the vascular response to injury in various disease states such as atherosclerosis and hypertension. It is clear that the vascular endothelium is a complex and dynamic organ. Understanding endothelium function in normal physiology and disease states is of potential clinical importance and should be the focus of future investigation.

Effects of amino acid infusion on renal hemodynamics. Role of endothelium-derived relaxing factor

Article

Jul 1991

Ingestion of protein or intravenous infusion of amino acids acutely elevates glomerular filtration rate (GFR) and renal plasma flow (RPF) by unknown mechanisms. Endothelium-derived relaxing factor (EDRF), now known to be nitric oxide derived from metabolism of L-arginine, participates in local regulation of vascular tone. To investigate the hypothesis that EDRF may participate in the renal vasodilatation and increased GFR after amino acid infusion, we characterized the effect of inhibition of EDRF synthesis with NG-monomethyl L-arginine (LNMMA) on basal renal hemodynamics and the response to infusion of a 10% mixed amino acid solution (1 ml/hr i.v.) in the rat. Renal arterial infusion of LNMMA (500 micrograms/kg/min) resulted in a significant increase in mean arterial pressure, decreases in GFR (20%) and RPF (44%), and a significant increase in filtration fraction. Pretreatment with the angiotensin II receptor antagonist Sar-Gly-angiotensin II did not prevent the increase in blood pressure but blunted the decreases in GFR (11%) and RPF (27%) after LNMMA infusion. Amino acid infusion in the untreated, fasted rat resulted in no change in blood pressure but significant increases in GFR and RPF; these effects were completely inhibited by intrarenal LNMMA but not an equihypertensive intravenous infusion of phenylephrine. In summary, EDRF participates in regulation of basal renal hemodynamics. Furthermore, amino acid-induced hyperfiltration and renal vasodilatation are completely prevented by inhibition of EDRF synthesis. We conclude that EDRF may participate in the renal hemodynamic response to amino acid infusion.

Endothelial derived relaxing factor (EDRF) controls renal hemodynamics in the normal rat kidney

Article

Jan 1991

These studies were conducted in the conscious, chronically catheterized rat to determine whether the endothelial derived relaxing factor (EDRF) controls renal function in the normal state. Administration of the EDRF synthesis inhibitors N-monomethyl-L-arginine (NMA; 100 mg/kg body weight) or N-nitro-L-arginine methylester (NAME; 10 mg/kg body wt) led to a large, sustained rise in blood pressure, a large rise in renal vascular resistance, a fall in renal plasma flow, a relatively slight reduction in glomerular filtration rate, and a consequent rise in filtration fraction. In addition, a marked natriuresis occurred because of a reduction in the fractional reabsorption of sodium. In separate studies, a continuous infusion of excess L-arginine (300 mg/kg body wt bolus followed by 50 mg/kg body wt per min) attenuated the NMA- or NAME-induced rise in blood pressure and reversed the renal hemodynamic effects such that a significant rise in renal plasma flow was seen. L-Arginine alone produced a selective renal vasodilation and large increases in sodium excretion. These observations support earlier suggestions that tonic release of EDRF controls the basal blood pressure and also show that renal function in the normal unstressed rat is markedly influenced by EDRF. These studies suggest that, in addition to controlling renal plasma flow, EDRF may have other, complex actions at the glomerulus. The natriuresis seen after acute inhibition of EDRF with NMA or NAME was probably the result of a pressure natriuretic response to the abrupt rise in blood pressure and also, perhaps, reflects removal of an EDRF influence to directly enhance sodium reabsorption somewhere in the nephron.

The endothelium. Target and promoter of hypertension?

Article

Jun 1990

T F Lüscher

Endothelium-derived relaxing factor influences renal vascular resistance

Article

Aug 1990
Am J Physiol

The mechanism of action of different vasodilators was investigated in the isolated perfused kidney of the rat. Acetylcholine (ACh, 10 nM-1 microM) and ATP (10 nM-1 microM), compounds known to relax isolated arteries in an endothelium-dependent fashion, caused concentration-dependent decreases in renal vascular resistance (RVR). Also, the endothelium-independent vasodilators verapamil (100 nM-10 microM), glyceryl trinitrate (GTN, 1-100 microM), and sodium nitroprusside (SNP, 1-100 microM) reduced RVR concentration dependently. Gossypol (10 microM, 5 min), an inhibitor of endothelium-derived relaxing factor (EDRF) production and/or release, increased basal RVR by 5% and significantly inhibited the vasodilator effects of ACh and ATP but had no effect on verapamil- or GTN-induced decreases in RVR. Methylene blue (MB) increased RVR dose dependently by up to 50%. About 50% of this effect could be antagonized with phentolamine (1 microM). MB abolished the relaxant response to ATP and attenuated the response to ACh. The dose-response curve of SNP was shifted to the right, and the relaxation to verapamil was slightly reduced. L-NG-methylarginine (100 microM) increased RVR by approximately 20%, and this effect was completely reversed by L-arginine (1 mM). N omega-nitro-L-arginine (100 microM) increased RVR by approximately 40% and attenuated the response to ATP but had no effect on the SNP-induced decrease in RVR. These results suggest that EDRF plays an important role in the regulation of RVR.

Effects of endothelium-derived relaxing factor and nitric oxide on rat mesangial cells

Article

Feb 1990
Am J Physiol

We have investigated whether endothelium-derived relaxing factor (EDRF) and nitric oxide (NO), a substance proposed to be one of the EDRFs, could elicit biochemical and biological responses in rat glomerular mesangial cells (MC). In wells with MC alone, guanosine 3',5'-cyclic monophosphate (cGMP) levels were 2.6 +/- 0.6 fmol/microgram protein, and bradykinin did not affect these levels, whereas in coincubation experiments with bovine aortic EC and rat MC, cGMP levels in MC increased to 44.6 +/- 21 fmol/micrograms protein after bradykinin stimulation (P less than 0.05). This effect was potentiated by superoxide dismutase and inhibited by hemoglobin and L-NG-monomethyl arginine, a specific inhibitor of EDRF synthesis. Increases in cGMP were also observed when MC were incubated directly with NO and were potentiated by superoxide dismutase and inhibited by hemoglobin. We also tested whether NO could inhibit angiotensin II (ANG II)-induced reductions in cross-sectional area (CSA) of MC. When MC were exposed to ANG II only, 65% of the cells underwent a significant reduction in CSA, as measured by digital image analysis. However, when MC were incubated with ANG II and NO, only 10% of cells responded (P less than 0.04). These studies demonstrate that EDRF and NO induce significant biochemical and functional responses in rat glomerular MC and suggest that communication between EC and MC may be important in regulation of glomerular function.

Role of endothelium-derived relaxing factor in regulation of renal hemodynamic responses

Article

Apr 1990
Am J Physiol

An endothelium-derived relaxing factor (EDRF) has recently been identified as nitric oxide (NO), originating from endothelial cell metabolism of L-arginine. In vitro studies suggest that EDRF/NO stimulates soluble guanylate cyclase and increases guanosine 3',5'-cyclic monophosphate (cGMP) levels in vascular smooth muscle cells, resulting in the vasorelaxant effects of endothelium-dependent vasodilators such as acetylcholine (ACh). The importance of EDRF/NO in normal physiology or disease states remains uncertain. We therefore investigated the relationship between ACh-induced hemodynamic responses, synthesis of EDRF/NO, and changes in the rate of urinary cGMP excretion in the anesthetized rat in vivo. Intravenous infusion of ACh resulted in hypotension, maintenance of glomerular filtration rate, and renal vasodilatation. ACh induced a dose-dependent increase in urinary cGMP excretion, an effect that was not observed with equihypotensive doses of the endothelium-independent vasodilator, prostacyclin. Rates of cGMP excretion were significantly correlated with the fall in systemic blood pressure induced by ACh. Treatment with NG-monomethyl-L-arginine (L-NMMA), an inhibitor of enzymatic synthesis of nitric oxide from L-arginine, prevented the ACh-induced increase in urinary cGMP excretion as well as the systemic and renal hemodynamic effects of ACh. Plasma levels of atrial natriuretic peptide were unchanged by ACh infusion. Intravenous infusion of L-NMMA was associated with increased blood pressure and decreased basal rates of urinary cGMP excretion. This hypertensive effect was reversed by administration of L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

L-NG-nitro arginine (L-NOARG), a novel, L-arginine-reversible inhibitor of endothelium-dependent vasodilatation in vitro

Article

Mar 1990

The effect of l ‐N G ‐nitro arginine ( l ‐NOARG) was compared with that of l ‐N G ‐monomethyl arginine ( l ‐NMMA) on vasodilatation of the isolated aorta of the rabbit and perfused mesentery of the rat in response to acetylcholine (ACh) and sodium nitroprusside (NP). l ‐NOARG (1.5–100 μ m ) and l ‐NMMA (3–100 μ m ) produced concentration‐related contraction of the rabbit aorta precontracted with phenylephrine (700–900 n m ). Similarly, l ‐NOARG (10–200 μ m ) and l ‐NMMA (30–100 μ m ) elevated perfusion pressure of the noradrenaline (NA, 0.6–2.5 m m )‐preconstricted rat mesentery preparation. l ‐NOARG (1.5–100 μ m ) and l ‐NMMA (3–100 μ m ) caused concentration‐related inhibition of the vasodilator effect of ACh (0.01–1.0 μ m ) on the rabbit aorta without influencing responses to NP (0.03–0.5 μ m ). l ‐NOARG methyl ester (30 μ m ) also inhibited ACh‐induced vasorelaxation with similar potency to NOARG. l ‐arginine (30–150 μ m ) but not d ‐arginine (100 μ m ) caused graded reversal of the inhibitory effect of both l ‐NOARG (15 μ m ) and l ‐NMMA (30 μ m ). Complete reversal of the effect of both inhibitors was achieved with 150 μ m l ‐arginine. l ‐Alanine (50 μ m ), l ‐arginosuccinic acid (5 μ m ), l ‐citrulline (50 μ m ), l ‐methionine (50 μ m ) and l ‐ornithine (50 μ m ) failed to reverse the inhibitory effect of l ‐NOARG (15 μ m ). l ‐NOARG (10–200 μ m ) and l ‐NMMA (30–100 μ m ) inhibited the vasodilator effect of ACh (0.006–18.0 nmol) in the rat mesentery without affecting vasodilatation due to NP (1.1–11.1 nmol). l ‐Arginine (100 μ m ) but not d ‐arginine (100 μ m ) produced partial reversal of the effect of l ‐NOARG (30 μ m ) and l ‐NMMA (30 μ m ). l ‐ and d ‐N α ‐butyloxycarbonyl N G ‐nitro arginine (100 μ m ) produced modest (approximately 20%) inhibition of the effect of ACh on the rabbit aorta; this effect was not reversible with l ‐arginine (100 μ m ). l ‐N α ‐monocarbobenzoxy arginine ( l ‐NMCA, 50 μ m ), l ‐N α ‐N G ‐dicarbobenzoxy arginine ( l ‐NDCA, 5 μ m ) and l ‐N G ‐tosyl arginine (50 μ m ) were inactive. These results identify l ‐NOARG as a potent, l ‐arginine reversible inhibitor of endothelium‐dependent vasodilatation. The available data suggests that l ‐NOARG, like l ‐NMMA, inhibits endothelial nitric oxide (NO) biosynthesis.

Inhibition of endothelial nitric oxide biosynthesis by N-nitro-L-arginine

Article

May 1990

1. The actions of N-nitro-L-arginine (NOLA) on the release of nitric oxide (NO) from arterial endothelial cells was studied in rat isolated thoracic aortic rings and by bioassay of NO derived from cultured bovine aortic endothelial cells. 2. NOLA (3–10 μmol/L) caused concentration-dependent inhibition of acetyl-choline-induced relaxation of phenylephrine-contracted rat aortic rings, which is dependent on the release of NO from the endothelium. The inhibitory actions of NOLA could be prevented by pre- and co-incubation with L-arginine (1 mmol/L). 3. Endothelium-independent relaxation induced by sodium nitroprusside was not affected by NOLA. 4. The release of NO from bovine aortic endothelial cells, induced by bradykinin (10 nmol/L), was detected by bioassay on pre-contracted rabbit aortic strips. NOLA (1–3 μmol/L, given through the cell column) reduced or abolished the release of NO, but did not affect relaxations of the bioassay tissues induced by glyceryl trinitrate or authentic NO. 5. These data indicate that NOLA potently inhibits the biosynthesis of NO from L-arginine, and thus prevents its release from arterial endothelial cells. It may be a useful pharmacological tool for probing the significance of NO biosynthesis in cardiovascular function.

Effects of NG-monomethyl-L-arginine and L-arginine on acetylcholine renal response

Article

Jul 1990

Intrarenal infusion of acetylcholine in meclofenamate-treated dogs significantly increased renal blood flow, diuresis, and natriuresis. Intrarenal infusions of either NG-monomethyl-L-arginine (inhibitor of endothelium-derived relaxing factor formation), or L-arginine (precursor of endothelium-derived relaxing factor formation) did not modify basal levels of those parameters. However, the infusion of NG-monomethyl-L-arginine inhibited the acetylcholine-induced increases in renal blood flow and diuresis without affecting natriuresis, which increased significantly. The infusion of L-arginine failed to further enhance hemodynamic and excretory effects elicited by acetylcholine. The concomitant infusion of L-arginine and NG-monomethyl-L-arginine did not change renal blood flow, urine flow, or sodium excretion rate. L-Arginine administration prevented the inhibitory effect of NG-monomethyl-L-arginine on acetylcholine-induced renal vasodilatation and diuresis. Glomerular filtration rate and mean arterial pressure did not change throughout the experiment. The results indicate that the vasodilatory and diuretic responses to intrarenal acetylcholine in meclofenamate-treated dogs are largely dependent on endothelium-derived relaxing factor.

Intrarenal Mechanisms That Regulate Sodium Excretion in Relationship to Changes in Blood Pressure

Article

Dec 1989

Because pressure-related natriuresis may be central to the regulatory role of the kidney on blood pressure, it is important to understand the relationship of humoral systems involved in the control of renal hemodynamics and tubular function. The preglomerular endothelial synthesis of prostaglandin I2 and endothelium-derived relaxing factor seem to modulate autoregulatory control by the afferent arterioles and the release of renin by the juxtaglomerular apparatus. The release of renin is followed by an increase in angiotensin II in the renal interstitium, which is responsible for adjusting the vascular tone of the efferent arterioles and vasa recta and for stimulating proximal tubular reabsorption of sodium. Variations in medullary circulation induced by angiotensin II could alter medullary interstitial pressure and the medullary production of prostaglandins E2 and I2 and, ultimately, could modulate sodium reabsorption in the medullary thick ascending limbs and the collecting ducts.

Ignarro LJ, Buga GM, Wood KS, Bryns RE, Chaudhuri GEndothelium-derived relaxing factor produced and released from artery and vein is nitric oxide. Proc Natl Acad Sci USA 84:9265-9269

Article

Jan 1988

A novel citrulline-forming enzyme implicated in the formation of nitric oxide by vascular endothelial cells

Article

Feb 1989

An enzyme in homogenates of porcine vascular endothelial cells forms L-citrulline from L-arginine. This enzyme is soluble and NADPH-dependent. In addition, the enzyme is inhibited by NG-monomethyl-L-arginine, suggesting that it is involved in the formation of nitric oxide by vascular endothelial cells.

A specific inhibitor of NO formation from L-arginine attenuates endothelial dependent relaxation

Article

Mar 1989

The role of l ‐arginine in the basal and stimulated generation of nitric oxide (NO) for endothelium‐dependent relaxation was studied by use of N G ‐monomethyl l ‐arginine ( l ‐NMMA), a specific inhibitor of this pathway. l ‐Arginine (10–100 μ m ), but not d ‐arginine (100 μ m ), induced small but significant endothelium‐dependent relaxations of rings of rabbit aorta. In contrast, l ‐NMMA (1–300 μ m ) produced small, endothelium‐dependent contractions, while its enantiomer N G ‐monomethyl‐ d ‐arginine (d‐NMMA; 100 μ) had no effect. l ‐NMMA (1–300 μ m ) inhibited endothelium‐dependent relaxations induced by acetylcholine (ACh), the calcium ionophore A23187, substance P or l ‐arginine without affecting the endothelium‐independent relaxations induced by glyceryl trinitrate or sodium nitroprusside. The inhibition of endothelium‐dependent relaxation by l ‐NMMA (30 μ m ) was reversed by l ‐arginine (3–300 μ m ) but not by d ‐arginine (300 μ m ) or a number of close analogues (100 μ m ). The release of NO induced by ACh from perfused segments of rabbit aorta was also inhibited by l ‐NMMA (3–300 μ m ), but not by d ‐NMMA (100 μ m ) and this effect of l ‐NMMA was reversed by l ‐arginine (3–300 μ m ). These results support the proposal that l ‐arginine is the physiological precursor for the basal and stimulated generation of NO for endothelium‐dependent relaxation.

Rapid increase in plasma and urine cGMP after bolus injection of atrial natriuretic factor in man

Article

Jan 1986

We studied the effects of a bolus injection of 50/micrograms synthetic human atrial natriuretic factor (ANF) on the cyclic GMP and cyclic AMP levels in plasma and urine of eight normal men. Administration of the hormone increased basal immunoreactive (IR-) ANF levels in plasma 2.8-fold to 110 pM three minutes after injection. Thereafter, IR-ANF levels rapidly declined to basal levels. Plasma cyclic GMP levels increased 2.6-fold to 16.6 nM within 6 minutes after ANF and decreased to near basal values within 30 minutes. Urinary cyclic GMP excretion increased 2.8-fold, whereas urinary volume and sodium excretion increased less than two-fold in the 30 minutes after ANF. Plasma cyclic AMP levels did not change. The data indicate that changes in plasma IR-ANF levels are followed by changes in plasma cyclic GMP and in urinary cyclic GMP excretion and suggest that cyclic GMP is a biological marker for circulating ANF in man.

Acetylcholine induces vasodilatation in the rabbit isolated heart through the release of nitric oxide, the endogenous nitrovasodilator

Article

Dec 1988

Acetylcholine (ACh, 0.03–3.0 μ m ) induced a dose‐dependent vasodilatation in the isolated Langendorff‐perfused heart of the rabbit. The vasodilatation was mimicked by exogenous nitric oxide (NO, 0.045–4.5 nmol). There was no detectable vascular relaxing activity in the cardiac effluent when these concentrations of ACh or NO were injected through the heart, even in the presence of an infusion of superoxide dismutase (SOD). Acetylcholine (0.03–3.0 μ m ), however, induced the release into the cardiac effluent of a material which produced a chemiluminescent signal when reacted with ozone, a response which could be mimicked with exogenous NO (0.045–4.5 nmol) injected through the heart. The effects of ACh, but not those of NO, were antagonized by atropine (2 μ m ). Prostacyclin (1 μ m ) injected through the heart induced vasodilatation without the release of a biologically active or chemiluminescent material. During passage through the heart, >99% of the biological activity of exogenous NO disappeared, whereas there was approximately 50% reduction of its chemiluminescent response. This indicates complete transformation into a mixture containing approximately 50% NO 2 ⁻ and 50% of other non‐chemiluminescent material(s), presumably NO 3 ⁻ . This study suggests that ACh induces endothelium‐dependent vasodilatation in the coronary circulation through the release of the endogenous nitrovasodilator, NO, which is rapidly converted to NO 2 ⁻ and NO 3 ⁻ .

Macrophage oxidation of L-Arginine to nitrite and nitrate: Nitric oxide is an intermediate

Article

Dec 1988

Previous studies have shown that murine macrophages immunostimulated with interferon gamma and Escherichia coli lipopolysaccharide synthesize NO2-, NO3-, and citrulline from L-arginine by oxidation of one of the two chemically equivalent guanido nitrogens. The enzymatic activity for this very unusual reaction was found in the 100,000g supernatant isolated from activated RAW 264.7 cells and was totally absent in unstimulated cells. This activity requires NADPH and L-arginine and is enhanced by Mg2+. When the subcellular fraction containing the enzyme activity was incubated with L-arginine, NADPH, and Mg2+, the formation of nitric oxide was observed. Nitric oxide formation was dependent on the presence of L-arginine and NADPH and was inhibited by the NO2-/NO3- synthesis inhibitor NG-monomethyl-L-arginine. Furthermore, when incubated with L-[guanido-15N2]arginine, the nitric oxide was 15N-labeled. The results show that nitric oxide is an intermediate in the L-arginine to NO2-, NO3-, and citrulline pathway. L-Arginine is required for the activation of macrophages to the bactericidal/tumoricidal state and suggests that nitric oxide is serving as an intracellular signal for this activation process in a manner similar to that very recently observed in endothelial cells, where nitric oxide leads to vascular smooth muscle relaxation [Palmer, R. M. J., Ashton, D. S., & Moncada, S. (1988) Nature (London) 333, 664-666].

Palmer RM, Rees DD, Ashton DS, Moncada SL-arginine is the physiological precursor for the formation of nitric oxide in endothelium-dependent relaxation. Biochem Biophys Res Commun 153:1251-1256

Article

Jul 1988

The formation of nitric oxide (NO) from L-arginine by vascular endothelial cells and its relationship to endothelium-dependent relaxation of vascular rings was studied. The release of NO, measured by bioassay or chemiluminescence, from porcine aortic endothelial cells stimulated with bradykinin was enhanced by infusions of L-, but not D-arginine. The release of 15NO, determined by high resolution mass spectrometry, from L-guanidino 15N (99%) arginine was also observed, indicating that NO is formed from the terminal guanidino nitrogen atom(s) of L-arginine. L-NG-monomethyl arginine (L-NMMA), but not D-NMMA, inhibited both the generation of NO by endothelial cells in culture and the endothelium-dependent relaxation of rabbit aortic rings. Both these effects were reversed by L-arginine. These data indicate that L-arginine is the physiological precursor for the formation of NO which mediates endothelium-dependent relaxation.

Comparative pharmacology of EDRF and nitric oxide on vascular strips

Article

Oct 1987
EUR J PHARMACOL

The comparative pharmacology of endothelium-derived relaxing factor (EDRF) and nitric oxide (NO) was studied on isolated strips of rabbit aorta. Both compounds were equally unstable. The relaxations of the bioassay tissues induced by EDRF released by bradykinin (3-100 nM) and by NO (4-134 nM) were indistinguishable. The stability of both compounds was increased to a similar extent by infusions of superoxide dismutase (SOD; 15 U.ml-1) or of cytochrome c (40 microM). The relaxations induced by EDRF and NO were inhibited to similar extents by infusions of Fe2+, hydroquinone and pyrogallol, an effect attenuated by a concomitant infusion of SOD or cytochrome c. The relaxations induced by both compounds were also inhibited by haemoglobin, however, this effect was unaltered by concomitant infusion of SOD. These data indicate that EDRF and NO have identical biological activity, stability and susceptibility to inactivation by superoxide anions and haemoglobin, providing further confirmation that EDRF is NO.

Endothelium-dependent vascular responses in normotensive and hypertensive Dahl rats

Article

Mar 1987

Experiments were designed to study endothelium-dependent responses in salt-sensitive (DS) and salt-resistant Dahl rats (DR). The rats were fed a low sodium (0.1% NaCl) or high sodium (8% NaCl) diet for 8 weeks. Blood pressure in DS fed a high sodium diet was higher than that in the remaining animals. Aortic rings with and without endothelium were suspended for isometric tension recording. Acetylcholine, adenosine 5'-diphosphate, and thrombin induced endothelium-dependent relaxations that were significantly depressed in the aorta of DS fed a high sodium diet. The relaxations in response to sodium nitroprusside were only slightly, but significantly, depressed in DS fed a high sodium diet. Removal of the endothelium greatly enhanced the response to serotonin and norepinephrine. In rings with, but not without, endothelium taken from rats fed a high sodium diet, the tension developed in response to serotonin and norepinephrine was significantly greater than that in animals fed a low sodium diet. These experiments indicate that endothelium-dependent relaxations to acetylcholine, adenosine 5'-diphosphate, and thrombin are depressed in hypertensive Dahl rats; this effect probably reflects a decreased release of endothelium-derived relaxing factor(s), although structural changes might contribute; and the responsiveness to vasoconstrictor agents is increased in DS and DR fed a high sodium diet. These findings may indicate differential effects of blood pressure and dietary salt on endothelial function.

Renal autoregulation, filtration rate, and electrolyte excretion during vasodilatation

Article

Oct 1970
Am J Physiol

Studies on the mechanism of natriuresis accompanying increased renal blod flow and its role in the renal response to extracellular volume expansion

Article

Dec 1965

The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine

Article

Dec 1980

Despite its very potent vasodilating action in vivo, acetylcholine (ACh) does not always produce relaxation of isolated preparations of blood vessels in vitro. For example, in the helical strip of the rabbit descending thoracic aorta, the only reported response to ACh has been graded contractions, occurring at concentrations above 0.1 muM and mediated by muscarinic receptors. Recently, we observed that in a ring preparation from the rabbit thoracic aorta, ACh produced marked relaxation at concentrations lower than those required to produce contraction (confirming an earlier report by Jelliffe). In investigating this apparent discrepancy, we discovered that the loss of relaxation of ACh in the case of the strip was the result of unintentional rubbing of its intimal surface against foreign surfaces during its preparation. If care was taken to avoid rubbing of the intimal surface during preparation, the tissue, whether ring, transverse strip or helical strip, always exhibited relaxation to ACh, and the possibility was considered that rubbing of the intimal surface had removed endothelial cells. We demonstrate here that relaxation of isolated preparations of rabbit thoracic aorta and other blood vessels by ACh requires the presence of endothelial cells, and that ACh, acting on muscarinic receptors of these cells, stimulates release of a substance(s) that causes relaxation of the vascular smooth muscle. We propose that this may be one of the principal mechanisms for ACh-induced vasodilation in vivo. Preliminary reports on some aspects of the work have been reported elsewhere.

Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP

Article

Apr 1983

The present study investigates the hypothesis that endothelium-dependent relaxation of vascular smooth muscle may be mediated through the formation of cGMP. Relaxation of the rat thoracic aorta to acetylcholine, histamine, and Ca++ ionophore A23187 was associated with increased levels of cGMP in a time- and concentration-dependent manner, whereas cAMP levels were unaltered. Removal of the endothelium prevented relaxation to these agents and prevented the increased levels of cGMP. Removal of the endothelium after exposure to acetylcholine only partially decreased the elevated levels of cGMP, suggesting that the changes in cGMP occurred within the smooth muscle cells. Eicosatetraynoic acid, an inhibitor of lipoxygenase and cyclooxygenase, and quinacrine, an inhibitor of phospholipase, prevented and reversed acetylcholine-induced relaxation, respectively, and inhibited acetylcholine-induced increased levels of cGMP. In contrast, sodium nitroprusside-induced relaxation and increased levels of cGMP were independent of the presence of the endothelium, exposure to eicosatetraynoic acid, and quinacrine. The present results support the hypothesis that vascular smooth muscle relaxation induced by some agents is dependent on the presence of the endothelium and is mediated through the formation of an endothelial factor that increases cGMP levels in smooth muscle.

A rapid method for the assay of nitrate in urine using the nitrate reductase enzyme of Escherichia coli

Article

Aug 1984
FOOD CHEM TOXICOL

Brent Bartholomew

A method was developed for urinary nitrate analysis utilizing an enzyme of Escherichia coli for the reduction of nitrate to nitrite. The resulting nitrite was assayed by a standard diazotization procedure. Under the experimental conditions stoichiometric conversion of nitrate to nitrite was achieved. Crude enzyme present in bacterial suspensions was used without any initial purification and no prior treatment of the urine samples was necessary. The bacteria were cultured under conditions producing high nitrate reductase activity and used formate as an exogenous electron donor without demonstrating any nitrite reductase activity. The procedure was subsequently automated to produce rapid, simultaneous determination of urinary nitrate and nitrite at the rate of 45 analyses/hr.

On the mechanism of angiotensin-induced proteinuria. I. Studies in aminonucleoside nephrotic rats and in saralasin blockade

Article

Feb 1981

Bauman, Jr., J.W

To test whether angiotensin (AII) induces proteinuria via its effect on renal hemodynamics, or by another mechanism, two experimental approaches were used. In the first, it was found that AII was as effective in inducing proteinuria in nephrotic as in intact rats. In all AII augmented proteinurias, filtration fraction was increased. These effects plus electrophoretic profiles of AII proteinuria in intact rats suggested that hemodynamic changes underly the increased glomerular permeability to protein. In the second approach, the AII inhibitor, sar-ala-angiotensin, does not itself induce proteinuria or changes in GFR and RPF, but prevented the hemodynamic responses to AII and the proteinuric response as well.

Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme A specific inhibitor of nitric oxide formation from L-arginine attenuates endothelium-dependent relaxation Inhibition of endothelial nitric oxide biosynthesis by N-nitro-L-arginine

Jan 1989
682-685418

D S Bredt
S H Snyder
D D Rees
R M J Palmer
H F Hodson
S Moncada

Bredt, D. S., and S. H. Snyder. 1990. Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme. Proc. Nall. Acad. Sci. USA. 87:682-685. 9. Rees, D. D., R. M. J. Palmer, H. F. Hodson, and S. Moncada. 1989. A specific inhibitor of nitric oxide formation from L-arginine attenuates endothelium-dependent relaxation. Br. J. Pharmacol. 96:418-424. 10. Dubbin, P. N., M. Zambetis, and G. J. Dusting. 1990. Inhibition of endothelial nitric oxide biosynthesis by N-nitro-L-arginine. Clin. Exp. Pharmacol. Physiol. 17:281-286.

Adaptation to increased dietary salt intake in the rat. Role of endogenous nitric oxide

Abstract

No full-text available

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