AJP Renal Physiology (Am J Physiol Ren Physiol)

Publisher: American Physiological Society (1887- ), American Physiological Society

Journal description

The American Journal of Physiology: Renal Physiology publishes original manuscripts on a broad range of subjects relating to the kidney, urinary tract, and their respective cells and vasculature, as well as to the control of body fluid volume and composition. Studies may involve human or animal models, individual cell types, and isolated membrane systems. Authors are encouraged to submit reports on research using a wide range of approaches to the study of function in these systems, such as biochemistry, immunology, genetics, mathematical modeling, molecular biology, and physiological methodologies. Papers on the pathophysiological basis of disease processes of the kidney, urinary tract, and regulation of body fluids are also encouraged.

Current impact factor: 4.42

Impact Factor Rankings

Additional details

5-year impact 0.00
Cited half-life 5.80
Immediacy index 0.99
Eigenfactor 0.05
Article influence 1.34
Website American Journal of Physiology - Renal Physiology website
Other titles American journal of physiology., Renal physiology, Renal physiology, AJP: renal physiology
ISSN 1522-1466
OCLC 40065092
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

American Physiological Society

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  • Conditions
    • NIH, Wellcome Trust, HHMI, MRC and BBSRC authors will on their behalf have the Publisher's version/PDF deposited in PubMed Central for release 12 months after publication
    • Publisher's version/PDF cannot be used
  • Classification
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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Lack or downregulation of the dopamine D2 receptor (D2R) results in increased renal expression of injury markers and pro-inflammatory factors that is independent of blood pressure increase. This study aimed to determine the mechanisms involved in the regulation of renal inflammation by D2Rs. Silencing D2Rs in mouse renal proximal tubule cells increased the expression of the pro-inflammatory TNFα, MCP-1, and IL-6. D2R downregulation also increased Akt phosphorylation and activity, and GSK3β phosphorylation and cyclin D1 expression both downstream Akt targets, however PI3K activity was not affected. Conversely D2R stimulation decreased Akt and GSK3β phosphorylation and cyclin D1 expression. Increased phospho-Akt, in the absence of increased PI3K activity, may result from decreased Akt dephosphorylation. Inhibition of PP2A with okadaic acid reproduced the effects of D2R downregulation on Akt, GSK3β and cyclin D1. PP2A catalytic subunit and the regulatory subunit PPP2R2C co-immunoprecipitated with the D2R. Basal phosphatase activity and the expression of PPP2R2C were decreased by D2R silencing that also blunted the increase in phosphatase activity induced by D2R stimulation. Similarly, silencing PPP2R2C also increased the phosphorylation of Akt and GSK3β. Moreover, downregulation of PPP2R2C resulted in increased expression of TNFα, MCP-1, and IL-6, indicating that decreased phosphatase activity may be responsible for the D2R effect on inflammatory factors. Indeed, the increase in NFkB reporter activity induced by D2R silencing was blunted by increasing PP2A activity with protamine. Our results show that D2R controls renal inflammation, at least in part, by modulation of the Akt pathway through effects on PP2A activity/expression. Copyright © 2014, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00453.2014
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    ABSTRACT: There have been two major theories surrounding the development of edema in nephrotic syndrome (NS), namely the under- and over-fill hypotheses. Edema is one of the cardinal features of NS and remains one of the principal reasons for admission of children to hospital. Recently, the discovery that proteases in the glomerular filtrate of patients with nephrotic syndrome are activating the epithelial sodium channel (ENaC) resulting in intrarenal salt retention and thereby contributing to edema might suggest that targeting ENaC with amiloride might be a suitable strategy to manage the edema of NS. Other potential agents, particularly urearetics and aquaretics might also prove useful in NS. Recent evidence also suggests that there may be other areas involved in salt storage, especially the skin, and it will be intriguing to study the implications of this in NS. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00229.2015
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    ABSTRACT: The architecture of the inner stripe of the outer medulla of human kidney has long been known to exhibit distinctive configurations; however, inner medullary architecture remains poorly defined. Using immunohistochemistry with segment-specific antibodies for membrane fluid and solute transporters and other proteins we identified a number of distinctive functional features of human inner medulla. In the outer inner medulla, AQP1-positive long-loop descending thin limbs (DTLs) lie alongside descending and ascending vasa recta (DVR, AVR) within vascular bundles. These vascular bundles are continuations of outer medullary vascular bundles. Bundles containing DTLs and vasa recta lie at margins of coalescing CD clusters, thereby forming two regions - the vascular bundle region and the CD cluster region. Although AQP1 and UT-B are abundantly expressed in long loop DTLs and DVR, respectively, their expression declines with depth below the outer medulla. Transcellular water and urea fluxes likely decline in these segments at progressively deeper levels. Smooth muscle myosin heavy chain protein is also expressed in DVR of the inner stripe and the upper inner medulla, but is sparsely expressed at deeper inner medullary levels. In rodent inner medulla, fenestrated capillaries abut CDs along their entire length, paralleling ascending thin limbs (ATLs), forming distinct compartments (interstitial nodal spaces, INSs); however, in the human this architecture rarely occurs. Thus, INSs are relatively infrequent in the human inner medulla, unlike the rodent where they are abundant. UT-B is expressed within the papillary epithelium of the lower inner medulla, indicating a transcellular pathway for urea across this epithelium. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00236.2015
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    ABSTRACT: This study was performed in order to investigate the immediate actions of the proinflammatory cytokines, interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), on the permeability of the glomerular filtration barrier (GFB) in rats and to test whether these actions are dependent upon the release of reactive oxygen species (ROS). In anaesthetized rats blood access was achieved and the left ureter was cannulated for urine collection. Rats were continuously infused i.v. with either IL-1β (0.4 and 2 μg·kg(-1)·h(-1)), TNF-α (0.4 and 2 μg·kg(-1)·h(-1)) or IL-6 (4 and 8 μg·kg(-1)·h(-1)), together with polydisperse fluorescein isothiocyanate (FITC)-Ficoll-70/400 and Inulin for 1 h. Plasma and urine samples were analyzed by high performance size exclusion chromatography (HPSEC) for determination of glomerular sieving coefficients (θ). The glomerular filtration rate (GFR) was also assessed ((51)Cr-EDTA). In separate experiments the superoxide scavenger, tempol (30 mg·kg(-1)·h(-1)), was given before and during cytokine infusions. IL-1β and TNF-α caused rapid, partly reversible increases in glomerular permeability to large molecules (Ficoll50-80Å), peaking at 5-30 min, while IL-6 caused a more gradual increase in permeability, leveling off at 60 min. Tempol almost completely abrogated the glomerular permeability effects of the cytokines infused. In conclusion IL-1β, TNF-α and IL-6, when infused systemically, caused immediate and partly reversible increases in glomerular permeability, which could be inhibited by the superoxide scavenger, tempol, suggesting an important role of ROS in acute cytokine induced permeability changes of the GFB. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00111.2015
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    ABSTRACT: Current therapies to limit kidney disease progression lack specificity and often have systemic toxicity. To approach this problem, we postulated that a human monoclonal antibody (F1.1), directed against the noncollagenous-1 domain (NC1) of α3(IV) collagen that localizes in glomeruli, could serve as vehicle for targeted drug delivery. Given enhanced exposure of NC1 domain of α3(IV) during glomerular diseases, with limited epitope expression in other organs, α3(IV)NC1 provides an ideal target for delivery of disease modifying agents. As a potential disease-modifying agent, we initially took advantage of recent observations that PGE2 promoted recovery after established injury during the course of nephrotoxic nephritis. To address the general applicability of the approach, the efficacy of glomerular delivery of dexamethasone was also examined. To achieve glomerular targeted therapy, PGE2 and dexamethasone were coupled to F1.1. After confirming composition and activity of the conjugates, both glomerular localization and the capacity of the conjugates to modify disease were evaluated. After injection to mice with established nephritis, resolution of disease was enhanced with both agents, with normalization of histology and improved BUN levels in conjugate treated mice, as compared to untreated mice. The results provide a novel means of targeting glomeruli during nephritis, irrespective of cause, by providing efficient drug delivery, with the potential of limiting systemic effects. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00289.2015
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    ABSTRACT: Hedgehog (Hh) is an evolutionary conserved signaling pathway that has important functions in kidney morphogenesis and adult organ maintenance. Recent work has shown that Hh signaling is reactivated in the kidney after injury and is an important mediator of progressive fibrosis. Pericytes and fibroblasts have been proposed to be the principal cells that respond to Hh ligands and pharmacological attenuation of Hh signaling has been considered as a possible treatment of fibrosis, but the effect of Hh inhibition on tubular epithelial cells after kidney injury has not been reported. Using genetically modified mice in which tubule-derived hedgehog signaling is increased and mice in which this pathway is conditionally suppressed in pericytes that express the proteoglycan Neuron-glial protein 2 (NG2), we found that suppression of Hh signaling is associated with decreased macrophage infiltration and tubular proliferation but also increased tubular apoptosis, an effect that correlated with the reduction of tubular β-catenin activity. Collectively our data suggest a complex function of hedgehog signaling after kidney injury in initiating both reparative and pro-proliferative, pro-survival processes. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00232.2015
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    ABSTRACT: We investigated obesity-induced changes in kidney lipid accumulation, mitochondrial function, and endoplasmic reticulum (ER) stress in the absence of hypertension, and the potential role of leptin in modulating these changes. We compared two normotensive genetic mouse models of obesity, leptin-deficient ob/ob mice and hyperleptinemic melanocortin-4 receptor deficient mice (LoxTB MC4R-/-), to their respective lean controls. Compared to controls, ob/ob and LoxTB MC4R-/- mice exhibit significant albuminuria, increased creatinine clearance and high renal triglyceride content. Renal ATP levels were decreased in both obesity models and mitochondria isolated from both models showed alterations that would lower mitochondrial ATP production. Mitochondria from hyperleptinemic LoxTB MC4R-/- mice kidneys respired NADH-generating substrates (including palmitate) at lower rates due to an apparent decrease in complex I activity, and these mitochondria showed oxidative damage. Kidney mitochondria of leptin-deficient ob/ob mice showed normal rates of respiration with no evidence of oxidative damage, but electron transfer was partially uncoupled from ATP synthesis. A 4-fold induction of C/EBP homologous protein (CHOP) expression indicated induction of ER stress in kidneys of hyperleptinemic LoxTB MC4R-/- mice. In contrast, ER stress was not induced in kidneys of leptin-deficient ob/ob mice. Our findings show that obesity, in the absence of hypertension, is associated with renal dysfunction in mice but not with major renal injury. Alterations to mitochondria that lower cellular ATP levels may be involved in obesity-induced renal injury. The type and severity of mitochondrial and ER dysfunction differs depending upon the presence or absence of leptin. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00188.2015
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    ABSTRACT: Vasopressin (VP) stimulates a signaling cascade resulting in phosphorylation and apical membrane accumulation of AQP2, leading to water reabsorption by kidney collecting ducts. However, the roles of most C-terminal phosphorylation events in stimulated and constitutive AQP2 recycling are incompletely understood. Here, we generated LLC-PK1 cells containing point mutations of all potential phosphorylation sites in the AQP2 C-terminus: S226, S229, T244, S256, S261, S264, and S269, to determine their impact on AQP2 trafficking. We produced an All Null AQP2 construct in which these serine (S) or threonine (T) residues were mutated to alanine (A) or glycine (G), and we then re-introduced the phosphorylation mimic, aspartic acid (D) individually to each site in the All Null mutant. As expected, the All Null mutant does not accumulate at the plasma membrane in response to VP, but still undergoes constitutive recycling as shown by its membrane accumulation when endocytosis is blocked by methyl-β-cyclodextrin (MβCD), and accumulation in a perinuclear patch at low temperature (20oC). Single phosphorylation mimics S226D, S229D, T244D, S261D, S264D, and S269D were insufficient to cause membrane accumulation of AQP2 alone or after VP treatment. However, AQP2 S256 reintroduced into the All Null mutant maintains its trafficking response to VP. We conclude that: a) constitutive recycling of AQP2 does not require phosphorylation at any C-terminal site; b) forced "phosphorylation" of sites in the AQP2 C-terminus is insufficient to stimulate membrane accumulation in the absence of S256 phosphorylation; c) phosphorylation of S256 alone is necessary and sufficient to cause membrane accumulation of AQP2. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00152.2015
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    ABSTRACT: Defects in primary cilia lead to a variety of human diseases. One of these, polycystic kidney disease, can be caused by defects in a Ca(2+)-gated ion channel (TRPP2) found on the cilium. Other ciliary functions also contribute to cystogenesis, and defects in apical Ca(2+) homeostasis have been implicated. By recording directly from the native cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin, we have identified a second Ca(2+)-gated channel in the ciliary membrane: the transient receptor potential cation channel, subfamily M, member 4 (TRPM4). In excised primary cilia, TRPM4 was found to have a low sensitivity to Ca(2+), with an EC50 of 646 μM at +100 mV. It was inhibited by MgATP and by 9-phenanthrol. The channel was not permeable to Ca(2+) or Cl(-) and had a permeability ratio PK/PNa of 1.42. Reducing the expression of Trpm4 mRNA with shRNA reduced the TRPM4 current by 87% and shortened primary cilia by 43%. When phospholipase C was inhibited, the sensitivity to cytoplasmic Ca(2+) greatly increased (EC50 = 26 μM at +100 mV), which is consistent with previous reports that PIP2 modulates the channel. MgATP did not restore the channel to a pre-inactivation state, suggesting that the enzyme or substrate necessary for making PIP2 is not abundant in primary cilia of mIMCD-3 cells. The function of TRPM4 in renal primary cilia is not yet known, but it is likely to influence the apical Ca(2+) dynamics of the cell, perhaps in tandem with TRPP2. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00294.2015
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    ABSTRACT: Maintenance of the glomerular filtration barrier with its fenestrated endothelium, the glomerular basement membrane and the podocytes as outer layer, is a major prerequisite for proper renal function. Tight regulation of the balance between plasticity and rigidity of the podocytes' architecture is required to prevent the onset of glomerular disease, mainly proteinuria. The underlying cellular signaling pathways that regulate the organization of the podocytes' cytoskeleton are still a matter of controversial debate. In this study we investigated the role of the NF-κB signaling pathway on podocyte cytoskeletal dynamics. As previously published, genetic inhibition of the NF-κB essential modulator (NEMO) in podocytes does not affect glomerular function under physiological, non-stressed conditions nor does it alter the initial podocyte response in an experimental glomerulonephritis (NTN)-model. Quite the contrary, podocyte-specific NEMO null mice recovered significantly faster and did not develop glomerulosclerosis and end-stage renale failure over time. Here, we show that cytoskeletal rearrangements and increased podocyte motility following stimulation with IL-1, TNFα or LPS depend on NEMO. NEMO also regulates the phosphorylation of the MAP kinase ERK1/2 and suppresses the activation of RhoA following stimulation with IL-1. The migratory response and altered ERK1/2 phosphorylation is independent of NF-κB signaling as demonstrated by expression of a mutant IκB resistant to phosphorylation and degradation. In conclusion, signaling through NEMO might not only be involved in the production of NF-κB pro-inflammatory chemokines but also regulates podocyte dynamics independent of NF-κB, most likely through small GTPases and MAP kinases. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00059.2015
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    ABSTRACT: In contrast to the negative feedback of angiotensin II (Ang II) on juxtaglomerular (JG) renin, Ang II stimulates renin in the principal cells of the collecting duct (CD) in rats and mice via Ang II type 1 (AT1R) receptor, independently of blood pressure. In vitro data indicate that CD renin is augmented by AT1R activation through PKC, but the exact mechanisms are unknown. We hypothesize that Ang II stimulates CD renin synthesis through AT1R via PKC and the subsequent activation of cAMP/PKA/CREB pathway. In M-1 cells, Ang II increased cAMP, renin mRNA (3.5 fold), prorenin and renin proteins, as well as renin activity in culture media (2 fold). These effects were prevented by PKC inhibition with calphostin C, PKC-alpha dominant negative and by PKA inhibition. Forskolin-induced increases in cAMP and renin expression were prevented by calphostin C. PKC inhibition and Ca2+ depletion impaired Ang II-mediated CREB phosphorylation and upregulation of renin. Adenylate cyclase 6 (AC) siRNA remarkably attenuated the Ang II-dependent upregulation of renin mRNA. Physiological activation of AC with vasopressin increased renin expression in M-1 cells. The results suggest that the Ang II-dependent upregulation of renin in the CD depends on PKCα, which allows the augmentation of cAMP production and activation of PKA/CREB pathway via AC6. This study defines the intracellular signaling pathway involved in the Ang II-mediated stimulation of renin in the CD. This is a novel mechanism responsible for the regulation of local RAS in the distal nephron. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00155.2015
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    ABSTRACT: This study describes fiber-type adaptations in hind-limb muscles, the interaction of the sex and the role of hypoxia on this response in 12 wk 5/6 nephrectomized rats (Nx). Contractile, metabolic and morphological features of muscle fiber-types were assessed in the slow-twitch soleus and the fast-twitch tibialis cranialis muscles of Nx rats, and compared with sham-operated controls. Rats of both sexes were considered in both groups. A slow-to-fast fiber-type transformation occurred in the tibialis cranialis of Nx rats, particularly in males. This adaptation was accomplished by impaired oxidative capacity and capillarity, increased glycolytic capacity and no changes in size and nuclear density of muscle fiber-types. An oxidative-to-glycolytic metabolic transformation was also found in the soleus muscle of Nx rats. However, a modest fast-to-slow fiber-type transformation, fiber hypertrophy and nuclear proliferation were observed in soleus muscle fibers of male, but not of female, Nx rats. Serum testosterone levels decreased by 50% in male but not in female Nx rats. Hypoxia-inducible factor-1α protein level decreased by 42% in the tibialis cranialis muscle of male Nx rats. These data demonstrate that 12 wk of Nx induces a muscle-specific adaptive response in which myofibers do not change (or enlarge minimally) in size and nuclear density, but acquire markedly different contractile and metabolic characteristics, which are accompanied by capillary rarefaction. Muscle function and sex play relevant roles in these adaptations. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00195.2015
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    ABSTRACT: Autoregulation of renal blood flow (RBF) is an essential function of the renal microcirculation that has been previously shown to be blunted by excessive dietary salt. Endogenous endothelin 1 (ET-1) is increased following a high salt (HS) diet and contributes to the control of RBF but the differential effects of ET-1 on renal microvessel autoregulation in response to HS remain to be established. We hypothesized that a HS diet increases endothelin receptor activation in normal Sprague-Dawley rats and blunts autoregulation of RBF. The role of ET-1 in the blunted autoregulation produced by a HS diet was assessed in vitro and in vivo using the blood-perfused juxtamedullary nephron preparation and anesthetized rats, respectively. Using highly selective antagonists, we observed that blockade of either ETA or ETB receptors was sufficient to restore normal autoregulatory behavior in afferent arterioles from HS fed rats. Additionally, normal autoregulatory behavior was restored in vivo in HS fed rats by simultaneous ETA and ETB receptor blockade whereas blockade of ETB receptors alone showed significant improvement of normal autoregulation of RBF. Consistent with this observation, autoregulation of RBF in ETB receptor deficient rats fed HS was similar to both ETB-deficient rats and transgenic control rats on NS diets. These data support the hypothesis that endogenous ET-1, working through ETB and possibly ETA receptors, contributes to the blunted renal autoregulatory behavior in rats fed a HS diet. Copyright © 2014, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 08/2015; DOI:10.1152/ajprenal.00641.2014
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    ABSTRACT: Heme oxygenase (HO) is a renoprotective protein in the microsome that degrades heme and produces biliverdin. Biliverdin is then reduced to a potent antioxidant bilirubin by biliverdin reductase in the cytosol. Because HO activity does not necessarily correlate with HO mRNA or protein levels, a reliable assay is needed to determine HO activity. Spectrophotometric measurement is tedious and requires a relatively large amount of kidney samples. Moreover, bilirubin is unstable and spontaneously oxidized to biliverdin in vitro. We developed a novel and sensitive LC-MS/MS method to quantify biliverdin to measure HO activity in mice. Biliverdin and its internal standard, a deuterated biliverdin-d4, have tandem mass spectrometry fragments with m/z transitions of 583 to 297 and 587 to 299, respectively. We prepared lysates of mouse kidneys, and added excess hemin, NADPH, and bilirubin oxidase to convert all bilirubin produced to biliverdin. After 30 min incubation at 37°C or 4°C, the samples were analyzed by LC-MS/MS. The difference in the amount of biliverdin between the 2 temperatures is HO activity. Treating mice with cobalt protoporphyrin, which induces the expression of HO, increased HO activity determined by biliverdin production. Measuring the production of biliverdin using LC-MS/MS is a more sensitive and specific way to determine HO activity than the spectrophotometric method, and allows the detection of subtle changes in renal or other HO activity. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00210.2015
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    ABSTRACT: The mechanisms regulating proximal tubule ammonia metabolism are incompletely understood. The current studies address the role of the proximal tubule basolateral, electrogenic, sodium-coupled bicarbonate cotransporter, NBCe1 (Slc14a4), in renal ammonia metabolism. We used mice with heterozygous and homozygous NBCe1 gene deletion, and compared these mice to their wild type littermates. Because homozygous NBCe1 gene deletion causes 100% mortality prior to day 25, we studied mice at day 8 (±1 day). Both heterozygous and homozygous gene deletion caused a gene dose-related decrease in serum bicarbonate. The ability to lower urinary pH was intact, and even accentuated, with NBCe1 deletion. However, in contrast to the well-known effect of metabolic acidosis to increase urinary ammonia excretion, NBCe1 deletion caused a gene dose-related decrease in ammonia excretion. There was no identifiable change in proximal tubule structure by light microscopy. Examination of proteins involved in renal ammonia metabolism showed decreased expression of phosphate-dependent glutaminase (PDG) and phosphoenolpyruvate carboxykinase (PEPCK), key enzymes in proximal tubule ammonia generation, and increased expression of glutamine synthetase, which recycles intrarenal ammonia and regenerates glutamine. Expression of key proteins involved in ammonia transport outside of the proximal tubule, Rhbg and Rhcg, was not significantly changed by NBCe1 deletion. We conclude from these findings that NBCe1 expression is necessary for normal proximal tubule ammonia metabolism. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00219.2015
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    ABSTRACT: We have previously shown that vasa recta pericytes are known to dilate vasa recta capillaries in the presence of PGE2 and contract vasa recta capillaries when endogenous production of PGE2 is inhibited by the non-selective NSAID, indomethacin. In this study, we have used a live, rat kidney slice model to build on these initial observations and provide novel data that demonstrates non-selective, COX-1- and COX-2-selective NSAIDs act via medullary pericytes to elicit a reduction of vasa recta diameter. Real-time images of in situ vasa recta were recorded and vasa recta diameter at pericyte and non-pericyte sites measured off-line. PGE2 and epoprostenol (a prostacyclin analogue) evoked dilation of vasa recta specifically at pericyte sites and PGE2 significantly attenuated pericyte-mediated constriction of vasa recta evoked by both ET-1 and Ang-II. NSAIDs, indomethacin>SC560>celecoxib>meloxicam, evoked significantly greater constriction of vasa recta capillaries at pericyte sites than at non-pericyte sites and indomethacin significantly attenuated the pericyte-mediated vasodilation of vasa recta evoked by both PGE2, epoprostenol, bradykinin and SNAP. Moreover, a reduction in PGE2 was measured using an enzyme immune assay following superfusion of kidney slices with indomethacin. In addition immunohistochemical techiques were employed to demonstrate the population of EP receptors in the medulla. Collectively, these data demonstrate that pericytes are sensitive to changes in PGE2 concentration and may serve as the primary mechanism underlying NSAID-associated renal injury and/or further compound associated tubular damage. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00199.2015
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    ABSTRACT: Although renin is a critical regulatory enzyme of the cardiovascular system, its roles in organogenesis and the establishment of cardiovascular homeostasis remain unclear. Mammalian renin-expressing cells are widespread in embryonic kidneys but highly restricted, specialised endocrine cells in adults. With a functional pronephros, embryonic zebrafish are ideal for delineating the developmental functions of renin-expressing cells and mechanisms governing renin transcription. Larval zebrafish renin expression originates in the mural cells of the juxtaglomerular anterior mesenteric artery and subsequently at extra-renal sites. The role of renin was determined by assessing responses to renin-angiotensin system blockade, salinity variation, and renal perfusion ablation. Renin expression did not respond to renal flow ablation, but was modulated by inhibition of angiotensin converting enzyme and altered salinity. Our data in larval fish is consistent with conservation of renin's physiologic functions. Using transgenic renin reporter fish, with mindbomb and cloche mutants, we show that Notch signalling and endothelium are essential for developmental renin expression. Following inhibition of angiogenesis, renin-expressing cells precede angiogenic sprouts. Arising from separate lineages, but relying on mutual interplay with endothelial cells, renin-expressing cells are amongst the earliest mural cells observed in larval fish, performing both endocrine and paracrine functions. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00247.2015
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    ABSTRACT: Purines induce transient contraction and prolonged relaxation of detrusor muscles. Transient contraction is likely due to activation of inward currents in smooth muscle cells, and prolonged relaxation may be due to activation of small conductance Ca(2+)-activated K(+) (SK) channels via P2Y1 receptors expressed by detrusor PDGFRα(+) cells. We investigated whether other subtypes of P2Y receptors are involved in the activation of SK channels in PDGFRα(+) cells of detrusor muscles. Quantitative analysis of transcripts revealed that P2ry2, P2ry4 and P2ry14 are expressed in PDGFRα(+) cells of P2ry1-/- /eGFP mice at similar levels as in wild type mice. UTP, a P2Y2/P2Y4 agonist, activated large outward currents in detrusor PDGFRα(+) cells. SK channel blockers and an inhibitor of phospholipase C completely abolished currents activated by UTP. In contrast, UTP activated non-selective cation currents in smooth muscle cells. Under current-clamp (I=0), UTP induced significant hyperpolarization of PDGFRα(+) cells. MRS2500, a P2Y1 antagonist, did not affect the UTP-activated outward currents in PDGFRα(+) cells from wild type, and activation of outward currents by UTP was retained in P2ry1-/-/eGFP mice. As a negative control, we tested the effect of MRS2693, a selective P2Y6 agonist. This compound did not activate outward currents in PDGFRα(+) cells, and currents activated by UTP were unaffected by MRS2578, a selective P2Y6 antagonist. Nonselective P2Y receptor blocker inhibited UTP-activated outward currents in PDGFRα(+) cells. Our data demonstrate that P2Y2 and/or P2Y4 receptors function, in addition to P2Y1 receptors in activating SK currents in PDGFRα(+) cells and possibly in mediating purinergic relaxation in detrusor muscles. Copyright © 2015, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00156.2015
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    ABSTRACT: Plasma Membrane Ca(2+)-ATPase's (PMCA) participate in epithelial Ca(2+) transport and intracellular Ca(2+) signaling. The Pmca4 isoform is enriched in distal nephron isolates and decreased in mice lacking the epithelial Ca(2+) channel, Trpv5. We therefore hypothesized that Pmca4 plays a significant role in transcellular Ca(2+) flux and investigated the localization and regulation of Pmca4 in Ca(2+)-transporting epithelia. Using antibodies directed specifically against Pmca4, we found it expressed only in the smooth muscle layer of mouse and human intestine, while pan-specific Pmca antibodies detected Pmca1 in lateral membranes of enterocytes. In kidney, Pmca4 showed broad localization to the distal nephron. In mouse, expression was most abundant in segments coexpressing the epithelial Ca(2+) channel, Trpv5. Significant, albeit lower expression, was also evident in the region encompassing the cortical thick ascending limbs, macula densa, and early distal tubules as well as smooth muscle layers surrounding renal vessels. In human kidney, a similar pattern of distribution was observed, with highest PMCA4 expression in NCC positive tubules. Electron microscopy demonstrated Pmca4 localization in distal nephron cells at both the basolateral membrane and intracellular perinuclear compartments, but not submembranous vesicles, suggesting rapid trafficking to the plasma membrane is unlikely to occur in vivo. Pmca4 expression was not altered by perturbations in Ca(2+) balance, pointing to a housekeeping function of the pump in Ca(2+) transporting epithelia. In conclusion, Pmca4 shows a divergent expression pattern in Ca(2+) transporting epithelia, inferring diverse roles for this isoform not limited to transepithelial Ca(2+) transport. Copyright © 2014, American Journal of Physiology - Renal Physiology.
    AJP Renal Physiology 07/2015; DOI:10.1152/ajprenal.00651.2014