Author:
Vanheel Bert,Calders Patrick,Van den Bossche Isabelle,Van de Voorde Johan
Abstract
The hyperpolarizing factor that is liberated by vascular endothelial cells in response to various agonists, and known to induce relaxation by opening of smooth muscle K+channels, has been suggested to be a product of cytochrome P450 dependent arachidonic acid metabolism. In this study, the direct influence of two phospholipase A2inhibitors and of five structurally and mechanistically different cytochrome P450 inhibitors on K+currents in freshly isolated vascular smooth muscle cells from the rat aorta was investigated. On stepping the cell membrane potential from -70 mV to a series of depolarized test potentials, a noisy outward current developed at test potentials > +10 mV, which showed no appreciable inactivation during the voltage pulse. It was largely abolished by 3 mM external tetraethylammonium chloride (TEA), suggesting that it predominantly consisted of current through large-conductance Ca2+-activated K+channels. The phospholipase A2inhibitor quinacrine considerably inhibited this TEA-sensitive current, while 4-bromophenacylbromide exerted no effect. The cytochrome P450 inhibitors proadifen and miconazole reversibly decreased the amplitude of IK, while clotrimazole and 1-aminobenzotriazole had no effect. Conversely, 17-octadecynoic acid increased whole-cell IK. These results show that some phospholipase A2and cytochrome P450 inhibitors may interfere with K+channel activation in the rat arterial smooth muscle cell. The relevance of these findings to studies on the involvement of cytochrome P450 dependent metabolism in the generation of the endothelium-derived hyperpolarizing factor in intact arteries is discussed.Key words: endothelial factors, smooth muscle, membrane currents, vasodilation, endothelium-derived hyperpolarizing factor (EDHF), arachidonic acid.
Publisher
Canadian Science Publishing
Subject
Physiology (medical),Pharmacology,General Medicine,Physiology
Cited by
10 articles.
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