propenylphosphonic-acid and 17-octadecynoic-acid

The endothelium plays an important role in maintaining vascular homeostasis by synthesizing and releasing several mediators of vasodilation, which include prostacyclin (PGI(2)), nitric oxide, and endothelium-derived hyperpolarizing factor (EDHF). We have recently defined the role of nitric oxide and PGI(2) in the dilation of submucosal intestinal arterioles from patients with normal bowel function. However, significant endothelium-dependent dilator capacity to ACh remained after inhibiting both these mediators. The current study was designed to examine the potential role of EDHF in human intestinal submucosal arterioles. ACh elicited endothelium-dependent relaxation in the presence of inhibitors of nitric oxide synthase and cyclooxygenase (23 +/- 10%, n = 6). This ACh-induced relaxation was inhibited and converted to constriction by catalase (-53 +/- 10%, n = 6) or KCl (-30 +/- 3%, n = 7), whereas 17-octadecynoic acid and 6-(2-propargylloxyphenyl) hexanoic acid, two inhibitors of cytochrome P450 monooxygenase, had no significant effect (3 +/- 1% and 20 +/- 8%, n = 5, respectively). Exogenous H(2)O(2) elicited dose-dependent relaxation of intact microvessels (52 +/- 10%, n = 7) but caused frank vasoconstriction in arterioles denuded of endothelium (-73 +/- 8%, n = 7). ACh markedly increased the dichlorofluorescein fluorescence in intact arterioles in the presence of nitric oxide synthase and cyclooxygenase inhibitors compared with control and compared with catalase-treated microvessels (363.6 +/- 49, 218.8 +/- 10.6, 221.9 +/- 27.9, respectively, P < 0.05 ANOVA, n = 5 arbitrary units). No changes in the dichlorofluorescein fluorescence were recorded in vessels treated with ACh alone. These results indicate that endothelial production of H(2)O(2) occurs in response to ACh in human gut mucosal arterioles but that H(2)O(2) is not an EDHF in this tissue. Rather, we speculate that it stimulates the release of a chemically distinct EDHF.

Topics: Acetylcholine; Adult; Aged; Caproates; Endothelium, Vascular; Fatty Acids, Unsaturated; Female; Humans; Hydrogen Peroxide; In Vitro Techniques; Intestines; Male; Microcirculation; Middle Aged; Vasodilation; Vasodilator Agents

Cytochrome P450 (CYP)-derived arachidonic acid metabolites, including epoxyeicosatrienoic acids (EETS) and 20-HETE, have been implicated in the regulation of renal function and vascular tone. Studying the function of specific CYP arachidonate metabolites has been hampered due to lack of selective inhibitors and difficulty in their solubilization. We have identified MS-PPOH as a potent and selective inhibitor of CYP-catalyzed arachidonate epoxidation in vitro. We used 2-hydroxypropyl-beta-cyclodextrin as a vehicle in order to administer MS-PPOH in vivo. One hour after administration, MS-PPOH (5 mg, IV bolus) significantly inhibited arachidonic acid epoxidation in rat renal cortical microsomes (vehicle-282 +/- 12 pmol/mg/min, MS-PPOH-206 +/- 10 pmol/mg/min, p < 0.05) but had no effect on 20-HETE formation (vehicle-383 32 pmol/mg/min, MS-PPOH-367 +/- 9 pmol/mg/min). The inhibitory effect lasts at least for 6 hours. There was no inhibition of 20-HETE synthesis at any time point. We also examined the effect of MS-PPOH on renal excretiry function. Three hours after MS-PPOH administration to anesthetized rats, urine flow rate became significantly higher (vehicle-275 +/- 16 microl/hour, MS-PPOH-406 +/- 44 microl/hour, p < 0.05). Sodium excretion rate was also significantly higher (vehicle-28.7 +/- 4 micromol/hour, MS-PPOH-63.3 +/- 10 micromol/hour, p < 0.05) but potassium excretion rate was not affected (vehicle-65.5 +/- 5 micromol/hour, MS-PPOH-79.2 +/- 2 micromol/hour). These results suggest that MS-PPOH may be useful as a selective inhibitor of CYP-catalyzed arachidonic acid epoxidation in vivo, and implicate EETs and anti-diuretic and anti-natriuretic in the regulation of renal function.

Topics: 8,11,14-Eicosatrienoic Acid; Amides; Animals; Arachidonic Acid; Chromatography, High Pressure Liquid; Cyclodextrins; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fatty Acids, Unsaturated; Humans; Immunoblotting; Kidney; Male; Miconazole; Microsomes; Organophosphorus Compounds; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Sulfones