Article

An extract of Desmodium adscendens inhibits NADPH‐dependent oxygenation of arachidonic acid by kidney cortical microsomes

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Cortical microsomes of human kidneys were used to study the effect of an extract of Desmodium adscendens on the cytochrome P450-dependent arachidonic acid (AA) metabolism. The phenolic compounds tyramine and hordenine, as well as triterpenoid saponins known to be present in the plant were also evaluated along with the extract, an n-butanol fraction (nBF) of the crude plant extract. The extract and the compounds were pre-incubated with the microsomal suspension before the addition of cofactors and radioactive AA. The products of the reactions and the unreacted AA were extracted, separtaed by HPLC and measured radiometrically. The total amount of radioactive AA converted, and the production of AA metabolites identified as epoxy-eicosatrienoic acids, monohydroxy-eicosatetraenoic acids, 19-, 20- and di-hydroxy derivatives of AA, were inhibited by nBF. The inhibition by nBF was shown to be dose-dependent. A saponin, sapogenin and the phenolic compounds present in D. adscendens did not inhibit this oxygenation of AA. The results indicate that this plant contains an as yet unidentified inhibitor for the third pathway of AA metabolism.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Parl as uite, parmi les saponines, trois composants très étudiése np harmacologie pour leur action agoniste sur certains canaux calciques, ont été isolés:la déhydrosoyasaponine I( DHS1), composé majoritaire et les soyasaponines Ie tI II [36]. On aa ussi isolé de la tyramine et de l'hordénine [37]. Plus récemment, a été identifié dans les feuilles et les tiges, un sucre, le d-pinitol [38]. ...
... D'autres étudessesont attachées àévaluerl'activité de fractions isolées d'un extrait aqueux de Da surles contractionsi nduites par différents produits (ovalbumine,a cide arachidonique, histamine, carbachol) sur tissusi solés. Ces travauxd é montrentq ue l'extrait aqueuxd eDa contient plusieurs types de substances actives qui agissent à différents niveaux dans la cascade de l'acide arachidonique, inhibant ainsi de manière efficace et synergique la libération de composésb roncho-constricteurs et d'antigènes,c eq ui confirmel 'activité antiasthmatique et antiallergique de cette espèce tout en précisants on mode d'action [37]. ...
... Besides these uses, healers in Congo have exploited D. adscendens as a cure for several diseases, including fever, pain, and epilepsy (6). It has been suggested that the action mechanism of the plant is due to the depletion of the histamine stocks (2); the inhibition of the ciclooxygenase and lipooxygenase enzymes (3); the increase of the prostaglandin synthesis, PGE 2 and PGF 2a ; the opening of the BKCa channels (25), and the inhibition of cytochrome P450 NADPH-dependent arachidonic acid metabolism (5). ...
Article
The pharmacological effects of aqueous extracts of Desmodium adscendens on selected immunological parameters were studied. This study deals with the evaluation of impact on the acute, subacute, and subchronic oral administrations of aqueous extracts of D. adscendens on both cellular and humoral immunity. The flow cytometry technique was used to determine the number of granulocytes, monocytes, and total lymphocytes, particularly TCD4+, TCD8+ and NK cells. The enzyme-linked immunosorbent assay method was used to measure the concentration of immunoglobulins (A, E, and G). The results clearly demonstrated that the aqueous extracts of D. adscendens affect the immune system. It decreased the counts of the total lymphocytes, particularly TCD4+, TCD8+, and NK cells, decreased the humoral immunity, and increased the monocyte counts. Aqueous extracts of D. adscendens have potentially strong effects on both cellular and humoral immunity, thus explaining its extensive traditional uses.
Article
Ethnopharmacological relevance: Plants of the genus Desmodium (Fabaceae), such as Desmodium styracifolium (Osbeck) Merr. and Desmodium gyrans (L. f.) DC., have a long history of medical use in Traditional Chinese Medicine to treat various ailments including rheumatism, pyrexia, dysentery, wounds, cough, malaria, hepatitis, hemoptysis, etc. In the theory of Traditional Chinese Medicine, most species have the effect of relieving internal heat or fever, neutralizing toxins, inhibiting pain, invigorating blood circulation, suppressing cough and alleviating dyspnea. Materials and methods: A bibliographic investigation was accomplished by analyzing secondary sources including Chinese Herbal Classics, and worldwide accepted scientific databases (Pubmed, Scopus and Web of Science, SciFinder) were scrutinized for the available information on the ethnopharmacological uses in Chinese medicine, phytochemistry, pharmacology and toxicology of Desmodium species. Results: The genus Desmodium is a large member of the Papilionaceae (Fabaceae) family. It contains about 350 plant species used for both feeding stuffs and herbal medicines, of which only about 30 species have been phytochemically or pharmacologically investigated. Desmodium plant extracts, as well as the active principles, have been experimentally studied for their anti-inflammatory, cytotoxic, antidiabetic, antinephrolithic, antibacterial, and nootropic activities in vitro or in vivo. And so far, a total of 212 compounds have been isolated from 15 Desmodium species and characterized mainly as flavonoids and alkaloids, followed by terpenoids, steroids, phenols, phenylpropanoids, glycosides and a number of volatile oils. The remaining unrevealed species are recorded chiefly in Asia and Africa being used in empirical treatment for various diseases. Conclusions: Desmodium species have long been used in TCM to treat various ailments. Available scientific references revealed that the traditional medical uses of some important Desmodium species in TCM have been evaluated by modern pharmacological studies. As literature demonstrated, flavonoids and alkaloids are perhaps responsible for most of the activities shown by the plants of this genus. Further studies are still required to reveal the structure-activity relationship of these active constituents.
Article
Desmodium gangeticum (L.) DC. and Desmodium adscendens (Sw.) DC. are two important and well explored species of genus Desmodium (Fabaceae (alt. Leguminosae) subfamily: Faboideae). Desmodium gangeticum is used as a tonic, febrifuge, digestive, anticatarrhal, antiemitic, in inflammatory conditions of chest and in various other inflammatory conditions in the Ayurvedic System of Medicine while Desmodium adscendens is widely used for the treatment of asthma in Ghana, Africa. The aim of this review is to provide comprehensive information on the botany, traditional uses, phytochemistry, pharmacological research and toxicology of Desmodium gangeticum and Desmodium adscendens to explore their therapeutic potential and future research opportunities. All the available information on Desmodium gangeticum and Desmodium adscendens was collected via electronic search (using Pubmed, SciFinder, Scirus, Google Scholar, JCCC@INSTIRC and Web of Science) and a library search for articles published in peer-reviewed journals. About 25 different species of Desmodium including Desmodium gangeticum and Desmodium adscendens are used ethnomedicinally all over the world. Phytochemical research on Desmodium gangeticum and Desmodium adscendens has led to the isolation of alkaloids, pterocarpans, phospholipids, sterols, flavones and flavonoid glycosides from Desmodium gangeticum and triterpenoid saponins, phenylethylamines and indole-3-alkyl amines from Desmodium adscendens. Crude extracts, fractions and isolated components of Desmodium gangeticum and Desmodium adscendens showed a wide spectrum of in vitro and in vivo pharmacological activities like antileishmanial, immunomodulatory, antiasthmatic, smooth muscle relaxant, anti-inflammatory, anti-ulcer, cardio-protective, antidiabetic, antiamnesic, antiviral, antioxidant and hepatoprotective activities. Desmodium gangeticum and Desmodium adscendens have emerged as a good source of traditional medicine. Desmodium gangeticum possesses the ability to scavenge the free radicals generated during ischaemia and ischaemia reperfusion thereby preserving the mitochondrial respiratory enzymes that eventually lead to cardio-protection and has potential prophylactic and therapeutic efficacy against Leishmania infection. Desmodium adscendens is useful against chronic bronchitis and asthma. However, there is a need to search for individual secondary metabolites responsible for these actions and study their mode of actions, bioavailability, pharmacokinetics and physiological pathways in sufficient detail. The promising results should be further substantiated by clinical trials.
Article
The effects of three chemically different groups of compounds, (triterpenoid saponins, beta-phenylethylamines and tetrahydroisoquinolines), known to be present in Desmodium adscendens, on plasma membrane ion channel, cytochrome P450 NADPH-dependent oxygenation of arachidonic acid, and production of prostaglandins by the cyclooxygenase enzyme system, are described. The very high-conductance calcium-activated potassium ion channel, which is responsible for the maintenance of tone in smooth muscles, was activated by the saponins. The cytochrome P450 NADPH-dependent monooxygenase reaction, which produces epoxy- and hydroxylated eicosanoids from arachidonic acid metabolism, was inhibited by an analogue of the tetrahydroisoquinoline present in the plant. This analogue also acted as a reductant in the prostaglandin synthesizing system using microsomes from ram seminal vesicles. The same system was activated by the beta-phenylethylamines found in the plant material, with the formation of more prostaglandins, the type being dependent on the amount of cyclooxygenase enzyme used and the presence or absence of coenzyme.
Article
Large-conductance calcium-dependent potassium (maxi-K) channels play an important role in regulating the tone of airway smooth muscle and the release of bronchoconstrictive substances from nerves in the lung. Crude extracts of Desmodium adscendens, a medicinal herb used in Ghana as a treatment for asthma, inhibit binding of monoiodotyrosine charybdotoxin (125I-ChTX) to receptor sites in bovine tracheal smooth muscle membranes that have been shown to be associated with maxi-K channels. Using this assay, three active components have been purified and identified by NMR and MS. Comparison with authentic samples revealed the three active components as the known triterpenoid glycosides dehydrosoyasaponin I (DHS-I), soyasaponin I, and soyasaponin III. The most potent of these compounds, DHS-I, is a partial inhibitor of 125I-ChTX binding (Ki = 120 nM, 62% maximum inhibition). Inhibition of 125I-ChTX binding is primarily due to a decrease in the observed maximum number of binding sites, with a smaller decrease in affinity. DHS-I increases the rate of toxin dissociation from its receptor, suggesting that modulation of ChTX binding occurs through an allosteric mechanism. DHS-I reversibly increases the open probability of maxi-K channels from bovine tracheal smooth muscle incorporated into planar lipid bilayers when applied to the intracellular, but not the extracellular, side of the membrane at concentrations as low as 10 nM. In contrast, DHS-I had no effect on several other types of potassium channels or membrane transporters. This natural product is the first example of a high-affinity activator of calcium-dependent potassium channels and is the most potent known potassium channel opener.
Article
Full-text available
The chemical composition of plants can vary according to factors such as soil and time of collection. Desmodium adscendens (Sw.) D.C. var. adscendens (Papillionaceae) is a plant employed in the treatment of asthma in Ghana, Africa. Studies have shown that butanolic extract inhibits contraction of the ileum and trachea in guinea pigs. In Mato Grosso, this plant is used only in the treatment of ovarian inflammation. The objective of this work was to verify if the plant found in Mato Grosso also relaxes smooth muscle and to understand better its action. The cumulative application of the butanolic fraction relaxed the contraction maintained in the isolated anococcygeus of a rat, induced by high potassium, but not that induced by phenylephrine. Relaxation was not altered by methylene blue. The butanolic fraction reduced in a concentration-dependent way the maximum response of concentration-response curve to calcium in the anococcygeus muscle. The results suggest that the butanolic fraction acts, at least partly, through the blockade of voltage-sensitive Ca+2 channels.
Article
The effects of methanol extract and gallic acid (3,4,5-trihydroxybenzoic acid) of Orostachys japonicus A. Berger on hepatic drug metabolizing enzymes and lipid peroxidation were investigated in rats treated with bromobenzene. The methanol extract of Orostachys japonicus reduced the activities of phase I enzymes, aminopyrine N-demethylase and aniline hydroxylase, that had been increased by i.p. injection of bromobenzene. Gallic acid isolated from Orostachys japonicus also reduced the aniline hydroxylase activity, while it did not affect the aminopyrine N-demethylase activity. The methanol extract and gallic acid restored the activity of epoxide hydrolase which had been decreased by bromobenzene. Hepatic glutathione content was lowered, along with increase in hepatic lipid peroxide, by bromobenzene administration. The hepatic lipid peroxidation induced by bromobenzene was prevented with the methanol extract and gallic acid of Orostachys japonicus. However, the decrease in glutathione was not altered by gallic acid. The present results suggest that the methanol extract and gallic acid of Orostachys japonicus may protect liver from bromobenzene toxicity through, at least in part, inhibiting the cytochrome P450-dependent monooxygenase activities and enhancing the activity of epoxide hydrolase. Antioxidant effect also may contribute to the protection of Orostachys japonicus against the bromobenzene-induced hepatotoxicity.
Article
A collection of 32 botanically identified medicinal plants from the slopes of Mt. Cameroon made by two Swedish settlers in the beginning of the last century is described and the literature is followed up. The drug names were found to be unaltered during the century passed.
Article
Full-text available
When corneal microsomes were incubated with arachidonic acid in the presence of an NADPH-generating system, two biologically active metabolites of arachidonic acid were formed. The structure of one of the metabolites, compound C, was previously reported to be 12(R)-hydroxy-5,8,10,14-eicosatetraenoic acid and was found to be a potent inhibitor of the Na+/K+-ATPase in the cornea. The second metabolite, compound D, was found to be a potent vasodilator as well as having the property of stimulating protein influx into the aqueous humor of the eye. Following purification of compound D by thin layer chromatography and high pressure liquid chromatography, it was found to lack a UV chromophore in contrast to the previously reported cytochrome P-450-dependent metabolite. Mass spectrometric analysis using positive and negative ionization modes was carried out on derivatized compound D that had been synthesized from a mixture of labeled [( 5,6,8,9,11,12,14,15-2H8]) and unlabeled arachidonic acid incubated with corneal microsomes. The novel arachidonate metabolite had abundant fragment ions consistent with compound D being a monooxygenated derivative of arachidonic acid with a hydroxyl substituent at carbon 12 of the eicosanoid backbone; only seven deuterium atoms from [2H8]arachidonate were retained in the structure. Oxidative ozonolysis yielded a product indicating that the double bonds in metabolite D resided between carbons at positions 8 and 9 and positions 14 and 15 of the 20-carbon chain. Compound D was therefore characterized as 12-hydroxy-5,8,14-eicosatrienoic acid. Model compounds were synthesized from dimethyl malate with the hydroxy at the 12 position with both the R and S absolute configuration and with all double bonds of the cis configuration. Only the 12(R) isomer was found to be a potent vasodilator and to increase aqueous humor protein concentration, suggesting that the biologically active compound D was 12(R)-hydroxy-5,8,14-(Z,Z,Z)-eicosatrienoic acid. As this compound possesses proinflammatory properties, it may play a role in the wound-healing processes of corneal injury.
Article
Full-text available
Arachidonic acid is oxidized by a NADPH-dependent oxygenase of rat liver microsomes to a number of oxygen-containing products, which can be resolved by HPLC. Several of these products have been purified and characterized. They exhibit an absorbance in the UV region of the spectrum that has a maximum at approximately 235 nm, indicative of the presence of a conjugated diene function. Mass spectral analysis of the trimethylsilyl ether derivatives of the methyl esters of the hydrogenated and nonhydrogenated metabolites shows that they are the 9-, 11-, 12-, and 15-monohydroxy derivatives of arachidonic acid, the hydroxyicosatetraenoic acids (HETEs). Their UV absorbance and chromatographic properties suggest that these products possess cis,transdiene geometry characteristic of HETEs isolated from other mammalian sources. THe isolation of these isomeric HETEs suggests that cytochrome P-450 may play a role in the oxidative metabolism of arachidonic acid to physiologically and pharmacologically important hydroxylated unsaturated fatty acids.
Article
Cumulative concentration-response curves (CCRC) of histamine, carbachol and leukotriene D, (LTD4), and relaxation curves were used to evaluate the nature of the modulation of allergic airway smooth muscle contraction of Desmodium adrcendens fraction F1 (DAF1). DAM significantly increased the maximal contractions (Emax) of tracheal spirals for all three agonists, and significantly increased the pD, values for histamine and carbachol, but decreased that for LTD4. On lung parenchymal strips DAM had no significant effect on the shape of the CCRC, the pD, value or Emax for histamine and carbachol. A significant decrease in the pD, value for LTD4, was observed at DAM concentrations of 0.3 and 0.9mg/mL. At the higher concentration, the decrease was accompanied by an equally significant decrease in the Emax. DAF1 per se, caused relaxation of tracheal spirals. The results indicate that DAF1's effect includes a reduction in sensitivity and responsiveness to LTD4-induced contractions.
Article
Desmodium adscendens is used in Ghana for the management of asthma. The first fraction (F1), isolated from an aqueous extract of the plant material by flash chromatography, was evaluated for its anti-allergic properties using ovalbumin (OA)- and arachidonic acid (AA)-induced contractions of tracheal spirals and lung parenchymal strips from guinea pigs. F1 inhibited OA- and AA-induced contractions in both tissues dose-dependently. In the AA-induced contractions, F1 was more effective on the tracheal spirals than on the lung parenchymal strip. On the OA-induced contractions of tracheal spirals, there was enhancement of the early phase of the contraction in the absence of indomethacin. This effect, which was biphasic, was not seen when the tissues were pretreated with indomethacin. Higher concentrations of F1 were required to effect the same inhibition in the absence of indomethacin than in its presence. F1 inhibited all phases of OA-induced contractions of lung parenchymal strips by >80% at the highest concentration used (0.9 mg/mL). The results suggest that F1 inhibits both the cyclo-oxygenase and the lipoxygenase pathways of AA metabolism. F1 also appears to inhibit the release of arachidonic acid.
Article
A simple radioactive-substrate assay for prostaglandin synthase (EC 1.14.99.1), which uses t.l.c. to measure simultaneously different prostaglandins synthesized from one precursor substrate, was developed. Rabbit kidney-medulla prostaglandin synthase catalyses the formation of prostaglandin E2, prostaglandin F2alpha and prostaglandin D2 from arachidonic acid. Fractionation of crude homogenates indicated that the microsomal fraction possessed the highest specific activity of prostaglandin synthase, whereas the soluble fraction exhibited little enzyme activity but rather contained a heat-labile inhibitory macromolecular factor(s), which might be attributed to the serum albumin present in this fraction. The microsomal fraction possessed low intrinsic enzyme activity, but the actvity could be fully stimulated by the presence of both GSH (reduced glutathione) and a phenolic cofactor. Only cysteine could partially replace GSH, whereas other thiols were inactive and some were even inhibitory. A variety of phenolic compounds, including catecholamines, dopamine (3,4-dihydroxyphenethylamine), 5-hydroxytryptamine and quinol, were active in stimulating prostaglandin synthase. In all cases, the stimulation was reflected in the synthesis of all three prostaglandins with ratios not significantly altered by different phenolic cofactors. The synthesis of each of the different prostaglandins appeared to have similar pH optima. The enzyme system was not inhibited by thiol-group inhibitors or a variety of metal chelators except for cyanide and 8-hydroxyquinoline. Characterization of the kidney-medulla prostaglandin synthase system indicated that it exhibited properties similar to those of the enzyme system present in seminal vesicles.
Article
This chapter discusses prostaglandins and thromboxanes. The prostaglandins are C 20 acids formed from polyunsaturated fatty acids by oxygenation and cyclization. The thromboxanes, which were originally found in platelets, have now been identified in a variety of tissues. Rapid progress is being made in understanding their biological roles. Earlier studies on vascular and airway smooth muscle demonstrated that endoperoxides had unique effects that could not be attributed to conversion into the stable prostaglandins. Because aspirin, an inhibitor of endoperoxide formation, inhibits the second wave of aggregation, it was suggested that the endoperoxides play a role in the release reaction. The potency of the endoperoxides in causing contractions of the isolated rabbit aorta was of particular interest. However, the occurrence of thromboxanes is not limited to platelets. The transformation of arachidonic acid into thromboxane B 2 has also been observed in lung tissue, spleen, kidney, leukocytes, umbilical artery, and brain.
Article
The precise role of the kidney in spontaneous experimental hypertension is unknown. We have analyzed the rates of renal prostaglandin synthesis by utilizing a spontaneously hypertensive rat model. The synthetic rate of prostaglandin E2, prostaglandin F2alpha, and prostaglandin A2-like products was measured in vitro with renal microsomes. In the rabbit and rat there is a steep gradient of microsomal prostaglandin synthetase from papilla to cortex with highest activities in the papilla. Comparison of the activity of prostaglandin synthetase in medullary microsomes form normotensive and hypertensive rats showed accelerated synthesis in the spontaneously hypertensive rat. These differences appeared after several months of age, were statistically significant from 3 mo of age and, on the average, represented at least a twofold increase of in vitro activity. All classes of prostaglandins were involved with increased synthesis of prostaglandin E2, prostaglandin F2alpha and prostaglandin A2-like material. These data reenforce and extend previous work showing alterations of granularity and presumably prostaglandin synthesis in renal medullary intersitital cells in various experimental hypertensions. We also measured renal tissue content of prostaglandin E and prostaglandin A-prostaglandin B by radioimmunoassay. Swift and careful handling of the tissue was necessary to avoid extensive postmortem synthesis of prostaglandins. In rapidly-frozen medullary tissue only prostaglandin E was detectable in concentrations ranging from 10 to 200 pg/mg tissue. No significant differences were found in the medullary content of prostaglandin E in the control and hypertensive rats despite the increased rates of enzymatic synthesis. We conclude that renal prostaglandin synthesis is increased in renal medullary microsomes obtained from spontaneously hypertensive rat. This apparently occurs in response to the progressive development of hypertension since young animals did not show an increase Renal tissue prostaglandin E content did not increase and therefore appears to be a poor index of enhanced prostaglandin synthesis.
Article
Cytochrome P450-dependent arachidonic acid metabolism in human kidney cortex from several postmortem subjects has been characterized. Using HPLC and GC/MS, four cytochrome P450-arachidonic acid metabolites were tentatively but not unequivocally identified as epoxyeicosatrienoic acid (EET), dihydroxyeicosatrienoic acid (DHT) and 19- and 20-hydroxyeicosatetraenoic acids, suggesting the involvement of two major cytochrome P450 enzymes, epoxygenase and omega/omega-1 hydroxylases. This pattern of metabolism was similar to that found in rabbit and rat kidneys. The formation of these metabolites was dependent on the presence of NADPH and inhibited by IgG of NADPH-cytochrome P450 (c) reductase. Immunologic studies of renal cytochrome P450 epoxygenase demonstrated that antibodies prepared against human-purified hepatic cytochrome P450 epoxygenase recognized renal enzyme protein and inhibited the enzyme activity by 92%. In contrast, control immunoglobulin did not inhibit renal cytochrome P450 epoxygenase. Antibody inhibition of renal cytochrome P450 epoxygenase demonstrated a degree of conservation of both enzyme proteins between liver and kidney. Antibodies against lauric acid omega/omega-1 hydroxylases (P450 omega) inhibited the formation of omega/omega-1 hydroxylase products, 19- and 20-HETEs. Identical qualitative patterns of arachidonic acid metabolites were observed in all cortical microsomes studied. Interindividual variations were observed in the cytochrome P450-dependent arachidonic acid metabolism, and the activities ranged from 0.031 to 5.027 nmol arachidonic acid converted/mg protein/30 min. which is about a 150-fold difference. However, when the specific activities for total cytochrome P450-dependent arachidonic acid metabolism were calculated, two separate groups could be distinguished, high and low metabolizers of arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
Renal cytochrome P-450-dependent monooxygenases metabolize arachidonic acid to products some of which affect vascular tone and (Na+,K+)ATPase activity. We measured these metabolites in spontaneously hypertensive (SHR) and control normotensive Wister-Kyoto (WKY) rats. Systolic tail blood pressure in SHR increased from 112 to 202 mm Hg and in WKY from 97 to 136 mm Hg at 5 and 20 weeks respectively. Renal cortical and outer medullary microsomes were incubated with [14C]arachidonic acid; metabolites formed via the cytochrome P-450 pathway were defined as those dependent on NADPH, inhibited by SKF-525A, and unaffected by indomethacin. The P-450-dependent metabolites were higher in SHR vs WKY at 5, 7 and 11 weeks in the cortex and at 7 and 11 weeks in the outer medulla. In the outer medulla, the formation of these metabolites peaked at 7 weeks. Using reverse-phase HPLC, the cytochrome P-450-dependent metabolites were separated into three radioactive peaks: peak I had a retention time of 17.5 min and comigrated as 11,12-dihydroxyeicosatrienoic acid standard. Peak II had a retention time of 19 min and comigrated with omega-hydroxylation compounds. Peak III had a retention time of 27 min and comigrated with 11,12-epoxyeicosatrienoic acid. In the renal cortex, peak I was higher in SHR vs WKY at 5, 7, and 9 weeks and peak III at 5, 7, 9 and 11 weeks. In the outer medulla, peak I was higher in SHR at 5 and 7 weeks, and peaks II and III at 7 weeks. Cytochrome P-450 content in the renal cortex was always higher in SHR vs WKY. We conclude that renal cytochrome P-450-dependent metabolites of arachidonic acid may participate in the circulatory changes of SHR, particularly during the developmental stage.
Article
Arachidonic acid (AA) can be metabolized to epoxides and their corresponding diols via the cytochrome P450 epoxygenase pathway. We have compared the vascular activity of four synthetically prepared epoxyeicosatrienoic acids, i.e. 5,6-, 8,9-, 11,12- and 14,15-EET (2-20 microM) on the isolated perfused rat tail artery. The 5,6-EET was equipotent with acetylcholine in dose dependently reducing vascular resistance (ED50 = 3.4 +/- 0.5 microM). The 8,9-, 11,12- and 14,15-EETs of AA did not affect vascular resistance; neither did the 5,6-DHET and delta-lactone, hydrolysis products of 5,6-epoxide. We suggest that the 5,6-epoxide, in contrast to other cytochrome P450-derived products, contributes to the regulation of regional vascular tone.
Article
ASPIRIN reduces the adhesiveness to glass of platelets in citrated plasma1, reduces platelet aggregation by washed connective tissue fragments2, and inhibits the second wave of aggregation induced by ADP, adrenaline and thrombin3–5. Aspirin also inhibits the release from washed pig or human platelets of permeability factors which differ from 5-hydroxytrypt-amine and histamine and cause contraction of the guinea-pig ileum6. One of these factors could be prostaglandin E2 (PGE2). This compound increases vascular permeability7,8 and contracts guinea-pig ileum9. When washed human platelets are incubated with thrombin it is formed and appears extracellularly, together with prostaglandin F2a (PGF2a)10.The following experiments, which were initiated independently of those described in the accompanying two articles1 '·12, were designed to test whether aspirin and other anti-inflammatory drugs inhibit the production of prostaglandins, which may be important mediators of inflammation.The effects of aspirin and other drugs were investigated on the production of prostaglandins and “the release reaction” induced by thrombin, that is, release of 5-hydroxytryptamine, adenine nucleotide and lysosomal enzymes13. We looked for the release of a lysosomal phospholipase A (ref.
Article
Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.
Article
In normal kidneys the renal medulla very efficiently converts arachidonic acid to prostaglandins. Although the renal cortex has only trace amounts of cyclooxygenase activity, we report here the existence of an active cortical NADPH-dependent monooxygenase that converts arachidonate primarily into 19-hydroxy- and 20-hydroxyarachidonate as well as 19-ketoarachidonate and a dicarboxylic acid. The enzyme is presumably a cytochrome P-450 monooxygenase and demonstrated marked resistance to inhibition by 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A), metyrapone, and carbon monoxide. In the rabbit kidney these products are produced only by the cortex in the presence of NADPH and represent the major metabolic products of arachidonate metabolism.
Article
Epoxyeicosatrienoic acids, formed during the cytochrome P-450-catalyzed oxidation of arachidonic acid, react with a liver cytosolic epoxide hydrolase to form vicinal diols of eicosatrienoic acid. The role of this cytosolic enzyme, rather than a microsomal bound type, explains previous results illustrating the ability to accumulate epoxides during the in vitro aerobic steady state of oxidative metabolism of arachidonic acid by liver microsomes. The inability of the 5,6-epoxyeicosatrienoic acid to serve as a suitable substrate for this enzyme is discussed in light of recent studies concerning possible unique physiological functions for this metabolite.
Article
Arachidonic acid (AA)-induced pressor response and production of thromboxane YXB2, the stable metabolite of TXA2, prostaglandin (PG)-like substance (PLS) and 6-keto-PGF1 alpha the stable metabolite of prostacyclin (PGIs), were studied using isolated, perfused kidneys of 6- and 18-week old spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY), two-kidney, one clip hypertensive rats (RHR) and DOCA/salt hypertensive rats (DOCA/salt HR). The AA-induced pressor response and release of TXB2 were highest in the 6-week old SHR, whereas, the release of PLS and 6-keto-PGF 1 alpha was marked in the 18-wek old SHR and the established hypertensive stages of both RHR and DOCA/salt HR. In the kidneys of SHR and WKy, exogenous TXA2 induced a severe vasoconstriction and there was a positive correlation between the AA-induced pressor response and the release of TXB2 or PLS. Thus, the initiation of hypertension in SHR may follow an accelerated synthesis of TXA2 against PGI2 in response to stimuli which induce a release of AA.
Leukotrienes and slow reacting substances of anaphylaxis (SRS-A) Allergy 35 Enhanced thromboxane A2 biosynthesis in the kidney of spontaneously hypertensive rats during the development of hypertension
  • B Samuelsson
  • S Hammarstrom
  • R C Murphy
  • P Borgeat
Samuelsson, B., Hammarstrom, S., Murphy, R. C., and Borgeat, P. (1980). Leukotrienes and slow reacting substances of anaphylaxis (SRS-A). Allergy 35, 375. Schibouta, Y., Terashita, Z., Inada, Y., Nishikawa, K., and Kikuchi, S. (1981 1. Enhanced thromboxane A2 biosynthesis in the kidney of spontaneously hypertensive rats during the development of hypertension. Eur. J. Pharrnacol. 70, 247-256.
Inhibition of vasopressin (ADH)-stimulated water flow and adenylate cyclase in toad bladder by dihydroxyeicosatrie-noic acids (DHET), the spontaneous hydrolysis products of epoxieicosatrienoic acids (EET)
  • D Schlondorff
  • E Petty
  • J Oats
  • S D Levine
Schlondorff, D., Petty, E., Oats, J., and Levine, S. D. (1986). Inhibition of vasopressin (ADH)-stimulated water flow and adenylate cyclase in toad bladder by dihydroxyeicosatrie-noic acids (DHET), the spontaneous hydrolysis products of epoxieicosatrienoic acids (EET). Clin. Res. 34, 700A.
Leukotrienes: Mediators of immediate hypersensitivitiy reactions and inflammation Prostaglandins and thromboxanes
  • B Samuelsson
  • B Samuelsson
  • M Goldyne
  • E Grandstrorn
  • M Hamberg
  • S Hammarstrom
  • C Malmsten
Samuelsson, B. (1983). Leukotrienes: Mediators of immediate hypersensitivitiy reactions and inflammation. Science 220, Samuelsson, B., Goldyne, M., Grandstrorn, E., Hamberg, M., Hammarstrom:S., and Malmsten, C. (1978). Prostaglandins and thromboxanes. Ann. Rev. Biochern. 47,997-1029.