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Biomedical subjects

J Quilley

Publications and source records attributed to J Quilley.

At least 37 records · Page 2Linked to original sources
PubMed1996

Possible contribution of platelet cyclooxygenase to the renal vascular action of 5,6-epoxyeicosatrienoic acid.

5,6-Epoxyeicosatrienoic acid (5,6-EET), a cytochrome P450-dependent arachidonate product, is a substrate for cyclooxygenase (COX) and, in some vascular preparations, elicits COX-dependent vasodilation. In the blood perfused rat kidney, 5,6-EET causes COX-dependent renal vasoconstriction, whereas in the rat isolated kidney perfused with a physiological buffer, 5,6-EET produces dose-dependent vasodilation that is unaffected by indomethacin. We examined the possible contribution of platelet COX to the vasoconstrictor action of 5,6-EET. Incubation of labeled 5,6-EET with rat washed platelets yields additional products that elute between 14 to 17 min on high-performance liquid chromatography (HPLC) and cause constriction of the perfused kidney. Indomethacin decreased the formation of these products and reduced the vasoconstrictor capacity of the corresponding HPLC fractions. Thus, platelet COX can metabolize 5,6-EET to vasoconstrictor products that may contribute to the in vivo vasoconstrictor effect of this eicosanoid.

8,11,14-Eicosatrienoic Acid↗
PubMed1996

Role of phospholipase C and phospholipase A2 in the nitric oxide-independent vasodilator effect of bradykinin in the rat perfused heart.

The cytochrome P450-dependent component of the coronary vasodilator action of bradykinin which requires activation of K+ channels was examined in terms of the contribution of phospholipases in the rat Langendorff heart preparation. This component was isolated by inhibition of nitric oxide synthase with nitroarginine and cyclooxygenase with indomethacin, neither of which affects the coronary vasodilator action of bradykinin. However, nitroarginine elevated coronary perfusion pressure from approximately 40 to 130 mm Hg. The phospholipase C inhibitor, U73122 {1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl) amino)hexyl)-1H-pyrrole-2,5-dione}, reduced coronary vasodilator responses to bradykinin by greater than 80%. U73122 also diminished the coronary vasodilator action of cromakalim which activates ATP-sensitive K+ channels. The maleimide moiety of U73122 that has the capacity to affect K+ channels inhibited cromakalim-induced coronary vasodilation, but did not affect that to bradykinin. Inhibition of diacylglycerol lipase with RHC 80267 {1,6-bis-(cyclohexyloximinocarbonylamino)-hexane} was without an overall effect on coronary vasodilator responses to bradykinin. The cytosolic phospholipase A2 inhibitor, AACOCF3 {arachidonyl trifluoromethyl ketone¿} decreased responses to bradykinin by up to 90% whereas inhibitors of the secretory form of phospholipase A2 oleyloxyethyl phosphorylcholine and ONO-RS-082 {2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid} were less effective than either AACOCF3 or U73122. The phospholipase inhibitors demonstrated selectivity as they did not affect the coronary vasodilator responses to nitroprusside. We obtained additional evidence for the antiphospholipase activity of the inhibitors by demonstrating their capacity to suppress bradykinin-stimulated increases in the release of prostacyclin, measured as 6-keto prostaglandin F1 alpha. The phospholipase inhibitors did not affect cyclooxygenase activity as the ability of arachidonic acid to stimulate prostaglandin formation was unimpaired. These results indicate that the coronary vasodilator action of bradykinin is linked to the activities of both phospholipase C and A2.

Animals↗
PubMed1995

Cytochrome P450-dependent effects of bradykinin in the rat heart.

1. Vasodilator responses to bradykinin (BK) in the rat heart are reported to be independent of NO and cyclo-oxygenase/lipoxygenase products of arachidonic acid (AA). 2. We verified that inhibition of NO synthase with L-nitroarginine (50 microM) and cyclo-oxygenase with indomethacin (2.8 microM) were without effect on vasodilator responses to BK (10-1000 ng) in the Langendorff rat heart preparation. 3. L-Nitroarginine elevated perfusion pressure, signifying a crucial role of NO in the maintenance of basal vasculature tone. 4. In hearts treated with L-nitroarginine to eliminate NO and elevate perfusion pressure, vasodilator responses were reduced by inhibitors of cytochrome P450 (P450), clotrimazole (1 microM) and 7-ethoxyresorufin (1 microM). 17-Octadecynoic acid (17-ODYA 2 microM), a mechanism based inhibitor of P450-dependent metabolism of fatty acids, also reduced vasodilator responses to BK. 5. These results confirm that NO and prostaglandins do not mediate vasodilator responses to BK in the rat heart but suggest a major role for a P450-dependent mechanism via AA metabolism.

Animals↗
PubMed1994

Role of K+ channels in the vasodilator response to bradykinin in the rat heart.

1. The role of K+ channels in the nitric oxide (NO)-independent coronary vasodilator effect of bradykinin was examined in the Langendorff heart preparation in which nitroarginine was used to inhibit NO synthesis and elevate perfusion pressure; cyclo-oxygenase was inhibited with indomethacin. 2. The K+ channel inhibitors, tetraethylammonium, procaine and charybdotoxin, but not glibenclamide, further increased perfusion pressure suggesting a role for K+ channels, other than ATP-sensitive K+ channels, in the regulation of coronary vascular tone under the experimental conditions adopted here. 3. The non-specific K+ channel inhibitors, tetraethylammonium and procaine, reduced vasodilator responses to bradykinin and cromakalim but not those to nitroprusside in the perfused heart treated with nitroarginine and indomethacin. 4. Glibenclamide, an inhibitor of ATP-sensitive K+ channels, reduced vasodilator responses to cromakalim but did not affect those to bradykinin or nitroprusside. 5. Charybdotoxin, an antagonist of Ca(2+)-activated K+ channels, inhibited responses to bradykinin but did not affect those to cromakalim or nitroprusside. 6. Nifedipine inhibited vasodilator responses to bradykinin and cromakalim without affecting those to nitroprusside. 7. Inhibition of cytochrome P450 with clotrimazole reduced responses to bradykinin but did not modify those to cromakalim or nitroprusside. 8. These results suggest that bradykinin utilizes a Ca(2+)-activated K+ channel to produce vasodilatation in the rat heart.

Animals↗
PubMed1994

Relaxant responses of rabbit aorta: influence of cytochrome P450 inhibitors.

Based on the use of inhibitors, cytochrome P450 has been implicated in endothelium-dependent relaxant responses via metabolism of arachidonic acid (AA). However, the contribution of cytochrome P450 and its AA metabolites to the regulation of vascular tone has not been established due, in part, to questions of specificity of cytochrome P450 inhibitors which have not been extensively characterized in terms of their vascular effects. Consequently, we addressed the effects of several inhibitors on vasorelaxant responses of phenylephrine-contracted, rabbit, aortic rings to agents that utilize different transduction mechanisms to determine any actions unrelated to inhibition of cytochrome P450 and/or AA metabolism. Octadecynoic acid (2.5 and 5 microM), a mechanism-based inhibitor of cytochrome P450 metabolism of fatty acids, and eicosatetrayenoic acid (10 and 20 microM), an inhibitor of AA metabolism, were without effect on vasorelaxant responses to acetylcholine, sodium nitroprusside, isoproterenol and diazoxide. 7-Ethoxyresorufin (2-10 microM), a substrate for cytochrome P450, and clotrimazole (2.5-10 microM) which binds to the heme moiety of the enzyme, concentration-dependently reduced responses to acetylcholine but not the other agonists indicating an effect on nitric oxide synthesis although neither affected the conversion of L-arginine to L-citrulline by endothelial cells. SKF 525A (50-200 microM), the prototypical inhibitor of cytochrome P450, which is metabolized to an inhibitory intermediate, also reduced responses to acetylcholine and, in addition, impaired the vasorelaxant activities of isoproterenol and diazoxide.

Acetylcholine↗
PubMed1992

Contribution of NO and cytochrome P450 to the vasodilator effect of bradykinin in the rat kidney.

1. Inhibition of nitric oxide generation with Nw-nitro-L-arginine (nitroarginine) reduced vasodilator responses to bradykinin and acetylcholine and enhanced those to nitroprusside in the rat isolated perfused kidney, preconstricted with phenylephrine. 2. Inhibition of cyclo-oxygenase with indomethacin, decreased the vasodilator responses to bradykinin by approximately 25% without affecting those to acetylcholine or nitroprusside. 3. BW755c, a dual inhibitor of cyclo-oxygenase and lipoxygenase, reduced renal vasodilator responses to bradykinin, comparable to the effect of indomethacin suggesting an effect related to inhibition of cyclo-oxygenase rather than lipoxygenase. 4. ETYA, an inhibitor of all arachidonic acid metabolic pathways, markedly reduced vasodilator responses to bradykinin but was without effect on the renal vasodilatation induced by acetylcholine or nitroprusside. 5. Clotrimazole and 7-ethoxyresorufin, inhibitors of cytochrome P450, greatly attenuated vasodilator responses to bradykinin without affecting those to acetylcholine or nitroprusside. 6. These data suggest that the renal vasodilator response to bradykinin is subserved by arachidonic acid metabolites as well as nitric oxide, the former accounting for up to 70% of the vasodilator effect of bradykinin.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1991

Evidence against a role of arachidonic acid metabolites in autoregulatory responses of the isolated perfused kidney of the rat.

The role of arachidonic acid metabolites in renal autoregulatory responses to changes in pressure was examined in rat isolated perfused kidneys. We also studied the influence of diabetes, a condition associated with hyperfiltration and altered renal eicosanoid production, on autoregulatory responses. The perfused rat kidney demonstrated autoregulation of flow within a pressure range of 100-150 mm Hg, with no differences between diabetic and control rat kidneys. Nifedipine resulted in vasodilatation and loss of autoregulation. Inhibition of the cyclooxygenase pathway of arachidonic acid metabolism with indomethacin failed to alter autoregulatory capacity. Similarly, inhibition of lipoxygenase with BW755C or NDGA, or inhibition of cytochrome P450-dependent enzymes with NDGA, clotrimazole or 7-ethoxyresorufin were without effect on autoregulatory responses. In vivo treatment with stannous chloride to deplete renal cytochrome P450-dependent enzymes also failed to modify autoregulatory responses. These results argue against a role of arachidonic acid metabolites in autoregulation of perfusate flow in the isolated kidney.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1991

Contraction and relaxation of rat aorta in response to ATP.

Vascular responses to ATP were studied in aortic rings isolated from stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY). Low concentrations of ATP (10 nM to 10 microM) caused relaxation and high concentrations (0.1 mM to 10 mM) caused contraction. Both of these responses were accentuated by factors released from the endothelium. The endothelium-derived relaxing factor (EDRF) was blocked by NG-monomethyl-L-arginine (L-NMMA). This is the first time that it has been reported that ATP causes the release of an endothelium-derived contracting factor (EDCF). Its release was diminished but not completely blocked by cyclooxygenase inhibitors. Assays of muscle bath prostanoid composition indicated that ATP stimulation caused the release of prostaglandins I2 and E2 and thromboxane A2 from intact aortic rings. Evidence is presented that neither endothelin nor superoxide anion contributed to the EDCF. No difference was observed between WKY and SHRSP with regard to either the endothelial contributions to the response, or the direct action on vascular smooth muscle of ATP. High concentrations of ATP achieved intravascularly in hypoxia may cause vasospasm by release of endothelial prostanoids.

Adenosine Triphosphate↗
PubMed1991

Cytochrome P-450-dependent vasodilation of rat kidney by arachidonic acid.

Our previous studies indicated a role for cytochrome P-450-dependent enzymes in generating the mediators of the vasodilator effect of arachidonic acid (AA) in the preconstricted indomethacin-treated perfused kidney of the rat. We report that in vivo induction of cytochrome P-450 enzymes with 3-methylcholanthrene-beta-naphthoflavone or dexamethasone enhanced the renal vasodilator effect of AA in this experimental preparation. Conversely, depletion of cytochrome P-450 enzymes with stannous chloride or cobalt chloride diminished the vasodilator response to AA. Injection of AA resulted in the release of relaxant material into the renal effluent detected by superfusion of rabbit aortic rings. Inhibition of cytochrome P-450 with 7-ethoxyresorufin reduced the release of vasorelaxant material. Metabolism of labeled AA by the kidney revealed four peaks of radioactivity that were recovered from the renal effluent. The heights of these peaks were reduced by 7-ethoxyresorufin. These results provide further evidence for cytochrome P-450-dependent metabolism of AA to one or more vasodilator products by the rat kidney.

Animals↗
PubMed1991

Cytochrome P-450-dependent vasodilator responses to arachidonic acid in the isolated, perfused kidney of the rat.

Pretreatment of phenylephrine (0.5 microM)-preconstricted, isolated perfused kidneys of the male rat with indomethacin (2.8 microM) or BM 13.177 (20 microM) abolished the vasoconstrictor response to arachidonic acid (AA), uncovering a vasodilator response. BW 755C (25 microM), a dual cyclooxygenase/lipoxygenase inhibitor, did not modify the vasodilator effect of AA, whereas 5,8,11,14-eicosatetraynoic acid (10 microM), which blocks all pathways of AA metabolism, abolished AA-induced vasodilation, thus suggesting the involvement of nonlipoxygenase AA metabolites. Clotrimazole (0.7 microM) and 7-ethoxyresorufin (1 microM), both considered to be specific inhibitors of the cytochrome P-450 monooxygenase enzymes, inhibited the vasodilator effect, suggesting that AA-induced renal vasodilation is mediated by one or more cytochrome P-450-derived AA metabolites. None of these interventions affected the vasodilator responses to acetylcholine (100 ng) and nitroprusside (1 microgram). Denudation of the endothelium with CHAPS (10 mg/l) reduced the vasodilator responses to AA, suggesting a requirement of an intact endothelium, whereas inhibition of guanylate cyclase with methylene blue (10(-4) M) was without effect, suggesting that cGMP was not involved in the vasodilator response to AA. The AA-induced renal vasodilation was accompanied by the generation of biologically active material or materials released into the renal effluent, which relaxed endothelium-intact and endothelium-denuded rings of isolated aorta and mesenteric and celiac arteries of the rabbit. These results suggest that in the rat kidney, AA is metabolized by endothelial cytochrome P-450-dependent enzymes to vasodilator metabolites.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1990

Renal vascular responsiveness to arachidonic acid in experimental diabetes.

1. Isolated perfused kidneys from diabetic rats (duration 4-6 and 20-24 weeks) were more sensitive to the vasoconstrictor effects of arachidonic acid than kidneys from age-matched control rats. Sensitivity diminished with age in both control and diabetic groups. 2. The enhanced vasoconstrictor effect of arachidonic acid in diabetic rat kidneys was associated with increased conversion to prostaglandins. 3. The renal vasoconstrictor response to arachidonic acid in both groups was reduced by thromboxane A2/prostaglandin H2 receptor antagonism but not by inhibition of thromboxane synthase. 4. Diabetic rat kidneys were also more sensitive to the vasoconstrictor effects of the endoperoxide analogue, U46619, while vasoconstrictor responses to phenylephrine were not markedly different from those of control rat kidneys. 5. In conclusion, prostaglandin endoperoxides appear to mediate arachidonic acid-induced vasoconstriction in diabetic and control rat kidneys. The enhanced renal vasoconstrictor response to arachidonic acid in diabetic rats results from increased sensitivity to endoperoxides and increased formation of endoperoxides from arachidonic acid.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Study of tachyphylaxis to the vasoconstrictor effect of arachidonic acid in the isolated perfused kidney of the rat.

The isolated perfused kidney of the rat was used to address the development of tachyphylaxis to the vasoconstrictor effects of arachidonic acid. Repeated administration of arachidonic acid (3 micrograms at 10-min intervals) to the isolated kidney of the rat, perfused in situ with Krebs-Henseleit solution, led to the development of tachyphylaxis to the renal vasoconstrictor effects of arachidonic acid, using perfusion pressure changes as an index. Vasoconstrictor responses to either angiotensin or the endoperoxide analog, U46619, were unaffected by repeated administration of arachidonic acid. Associated with progressively reduced renal vasoconstrictor responses to arachidonic acid were parallel decrements in the renal venous release of prostanoids, measured by radioimmunoassay. In contrast, the release of prostanoids from the kidney stimulated by angiotensin II was increased after repeated administrations of arachidonic acid. These data suggest that the sequential reduction in renal vasoconstrictor responses to arachidonic acid is due to diminished conversion to prostaglandins, possibly due to inactivation of cyclooxygenase, decreased entry of arachidonic acid into the cell or its increased esterification into phospholipids.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Role of endoperoxides in arachidonic acid-induced vasoconstriction in the isolated perfused kidney of the rat.

1. Administration of arachidonic acid caused dose-dependent vasoconstriction in the isolated rat kidney perfused in situ with Krebs-Henseleit solution. 2. Inhibition of cyclo-oxygenase with indomethacin or meclofenamate reduced the renal vasoconstrictor effect of arachidonic acid. 3. The renal vasoconstrictor effect of arachidonic acid was unaffected by CGS-13080 at concentrations that effectively reduced thromboxane A2 (TxA2) synthesis by platelets and the kidney. 4. The endoperoxide/TxA2 receptor antagonist, SQ 29,548, abolished the renal vasoconstrictor effect of arachidonic acid and of U46619, an endoperoxide analogue. In contrast, SQ 29,548 did not affect the renal vasoconstrictor response to angiotensin II, prostaglandin E2 or F2 alpha. 5. These data suggest that the vasoconstrictor effect of arachidonic acid in the isolated kidney of the rat is mediated by its metabolites, including the prostaglandin endoperoxides.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Renal vascular responses and eicosanoid release in diabetic rats.

Changes in renal perfusion pressure and eicosanoid release in response to arginine vasopressin (AVP; 1-10 ng) and angiotensin II (ANG II; 1-10 ng) were determined 5 days, 2 wk, and 8-12 wk after the induction of diabetes with streptozotocin (STZ) in male Wistar rats. Renal perfusion pressure responses to AVP and ANG II were reduced at 2 and 8-12 wk, but not at 5 days, after the induction of diabetes. However, AVP- and ANG II-stimulated release of prostaglandins into the renal venous effluent was depressed at all times tested. Inhibition of cyclooxygenase with indomethacin did not significantly influence the perfusion pressure responses to ANG II and AVP. Likewise, raising perfusate glucose levels to 400 mg/dl or adding insulin (180 microU/ml) to the perfusate failed to modify responses to ANG II. In contrast, administration of 0.3 microgram arachidonic acid (AA), a dose approaching threshold in control rat kidneys, to the kidney of the diabetic rat resulted in a marked increase in perfusion pressure. Associated with the increase in renal perfusion pressure to AA in the diabetic rat were significant increases in renal venous efflux of prostaglandin E2 and prostacyclin compared with control. These data suggest a defect in renal deacylation-reacylation of AA associated with an increase in cyclooxygenase activity in the diabetic rat.

Angiotensin II↗
PubMed1987

The antihypertensive effect of captopril in essential hypertension: relationship to prostaglandins and the kallikrein-kinin system.

Two groups, each with nine essential hypertensive patients, were maintained on 10 mmol sodium daily over 14-17 days and treated in this sequence: placebo; captopril (25 or 50 mg given thrice daily) or indomethacin (50 mg given thrice daily) alone; captopril plus indomethacin, and (4) captopril alone. The initial fall in mean blood pressure induced by captopril (118 +/- 1 to 102 +/- 1 mmHg) was unaffected by the addition of indomethacin. However, if indomethacin treatment preceded captopril, the antihypertensive effect was attenuated (116 +/- 4 to 109 +/- 4), and was associated with significant reductions in urinary prostaglandin and kinin excretion. Addition of captopril to indomethacin returned kinin excretion to placebo levels but did not affect indomethacin-induced reduction in prostaglandin excretion. Captopril alone stimulated plasma renin activity (PRA) fivefold; aldosterone excretion was lowered by 25% and further reduced by indomethacin. Thus, when captopril and indomethacin are administered together, the order of administration is critical to the antihypertensive effect of captopril.

Adult↗
PubMed1987

Aspirin enhances the antihypertensive effect of captopril in spontaneously hypertensive rats.

Activation of renal or vascular prostaglandin mechanisms (or both) has been proposed to contribute to the antihypertensive action of captopril. In conscious spontaneously hypertensive rats (SHR) studied in the established phase of hypertension, the blood pressure-lowering effect of captopril, 30 mg/kg/12 hr p.o. given for 7 days, was greatly enhanced by the addition of aspirin, 200 mg/kg/day s.c. Systolic blood pressure decreased from 185 +/- 6 and 182 +/- 4 to 135 +/- 3 mm Hg in rats treated, respectively, with captopril and aspirin or captopril alone, and was unaltered by either vehicle or aspirin alone. Water intake was inconsistently affected by captopril but was increased (p less than 0.01) by aspirin and was even higher after captopril-aspirin treatment (p less than 0.01). Urine volume was elevated in all 3 drug-treated groups, increasing threefold after captopril-aspirin treatment. Excretion of sodium and potassium was unchanged by any treatment regimen. In the vehicle group, prostaglandin F2 alpha excretion, measured by radioimmunoassay, ranged between 65 and 93 ng/8 hr and was twofold to fourfold higher than that of prostaglandin E2. Prostaglandin F2 alpha was unaffected during captopril treatment, whereas prostaglandin E2 excretion decreased to 12 +/- 2 ng/8 hr (p less than 0.01) by Day 7. Long-term aspirin treatment, either with or without captopril, did not cause sustained inhibition of renal prostaglandin excretion, although a transient effect occurred within the first four hours of administration. These results indicate 1) aspirin potentiates the blood pressure-lowering effect of captopril in SHR, an effect that is associated with a threefold increase in urine flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Failure of chronic aspirin treatment to inhibit urinary prostaglandin excretion in spontaneously hypertensive rats: comparison with indomethacin and flurbiprofen.

The inability of chronic treatment with aspirin to cause sustained inhibition of urinary prostaglandin (PG) excretion observed previously prompted us to compare the effects of 9-day treatment of spontaneously hypertensive rats with aspirin, 200 mg/kg/day s.c., flurbiprofen, 2.5 mg/kg/b.i.d. s.c. and indomethacin, 2.5 mg/kg/b.i.d. s.c. on the excretion rate of radioimmunoassayable PGE2 and PGF2 alpha. Conversion of 1-[14C]arachidonic acid and the release of PGs from endogenous substrate by the renal papilla were also examined. In vehicle-treated control rats, PGF2 alpha excretion ranged from 32.2 +/- 6.2 (mean +/- S.E.M.) to 41.6 +/- 7.3 ng/6 h, and was 2- to 4-fold higher than that of PGE2. Within 6 h of administration all three drugs reduced excretion of PGF2 alpha and PGE2 to less than 20% and 35% of control rats, respectively. Thereafter, PGF2 alpha and PGE2 excretion in aspirin-treated rats returned to values similar to the vehicle-treated group, whereas inhibition of PG excretion in indomethacin and flurbiprofen groups was sustained. Urine volume was doubled by aspirin throughout the study. In contrast, urine volume in flurbiprofen- and indomethacin-treated rats was unaffected. Paradoxically, metabolism of 1-[14C]arachidonic acid to PGs by renal papilla dissected on day 10, 2 to 4 h after the last drug dose, was reduced markedly by aspirin as was the release of immunoreactive PGs but was unaffected by flurbiprofen or indomethacin. The failure of long-term aspirin treatment to inhibit urinary PG excretion and the disparity between in vivo and ex vivo indices of PG release emphasize the need to verify their intended action by measuring PGs in biological fluids.

Animals↗