Acetylcholine-induced relaxation and hyperpolarization in small bovine adrenal cortical arteries: role of cytochrome P450 metabolites.
The present study characterizes the vascular responses of isolated small bovine adrenal cortical arteries to acetylcholine, an endogenous neurotransmitter in the adrenal gland. Acetylcholine (10(-10) to 10(-6) m) elicited a concentration-dependent relaxation, with a maximal relaxation of 96 +/- 1% and EC50 of 4.2 nm. The relaxation was abolished by endothelial removal and attenuated by the nitric oxide synthase inhibitor N-nitro-L-arginine (L-NA, 30 microm) but not by the cyclooxygenase inhibitor indomethacin (10 microm). The maximal relaxation and EC50 of acetylcholine in the presence of L-NA were 87 +/- 4% and 22 nm, respectively. The acetylcholine-induced, indomethacin- and L-NA-resistant relaxation was eliminated by high K+ and markedly inhibited by the cytochrome P450 inhibitors SKF 525A (10 microm) and miconazole (10 microm). The maximal relaxations and EC50s with SKF 525A and miconazole were 56 +/- 8 and 72 +/- 2% and 0.8 and 0.5 microm, respectively. In indomethacin- and L-NA-treated arteries, acetylcholine induced a smooth muscle hyperpolarization, which was blocked by SKF 525A (3 +/- 1 mV vs. 15 +/- 2 mV of control). Arachidonic acid (10(-9) to 10(-5) m) and 14,15-epoxyeicosatrienoic acid (14,15-EET, 10(-9) to 10(-5) m), a cytochrome P450 metabolite of arachidonic acid, also evoked relaxations in small adrenal arteries, with maximal relaxations of 56 +/- 4 and 90 +/- 5%, respectively. The arachidonic acid-induced relaxation was blocked by SKF 525A. Using high-pressure liquid chromatography and gas chromatography/mass spectrometry analysis, EETs were identified in small adrenal arteries. These results demonstrate that acetylcholine is a potent vasodilator of small adrenal cortical arteries. The acetylcholine-induced relaxation is largely mediated by an endothelium-dependent hyperpolarization mechanism, presumably through cytochrome P450 metabolites of arachidonic acid.
Zhang
David X
DX
Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
Gauthier
Kathryn M
KM
Campbell
William B
WB
D000109:Acetylcholine / Q000494:pharmacology*; D000302:Adrenal Cortex / Q000098:blood supply*; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004351:Drug Resistance; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D019335:Nitroarginine / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D019335:Nitroarginine; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D000109:Acetylcholine; D007213:Indomethacin