beta-Adrenoceptor-mediated relaxation inhibited by tetrapentylammonium ions in rat mesenteric artery
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AbstractThe aim of this study was to examine the contribution of K+ channel activation to beta-adrenoceptor-mediated relaxation in rat mesenteric arteries. Isoprenaline and fenoterol concentration-dependently relaxed the phenylephrine-preconstricted endothelium-intact arteries of the rat with EC50 values of 0.26 +/- 0.03 mu M and 0.87 +/- 0.12 mu M, respectively. beta-Adrenoceptor-mediated relaxation was significantly attenuated upon removal of endothelium. Tetrapentylammonium ions (TPA(+)) at low concentrations (1-5 mu M) inhibited relaxations induced by beta-adrenoceptor agonists in arteries with and without endothelium, while glibenclamide (3 mu M) had no effect. TPA(+) (5 mu M) inhibited isoprenaline-induced relaxation in the presence of either iberiotoxin (100 nhl) or glibenclamide (3 mu M) TPA(+) did not alter forskolin-induced relaxation. In the presence of 60 mM extracellular K+, the relaxations induced by two agonists were reduced in endothelium-intact arteries and abolished in endothelium-denuded arteries. The present results suggest that the activation of TPA(+)-sensitive K+ channels contributes toward the relaxations mediated through beta- and beta(2)-adrenoceptor stimulation in rat mesenteric arteries. (C) 1998 Elsevier Science Inc.
All Author(s) ListHuang Y, Kwok KH
Journal nameLife Sciences
Volume Number62
Issue Number2
LanguagesEnglish-United Kingdom
Keywordsbeta-adrenoceptor-mediated relaxation; K+ channels; mesenteric arteries; tetrapentylammonium ions
Web of Science Subject CategoriesMedicine, Research & Experimental; MEDICINE, RESEARCH & EXPERIMENTAL; Pharmacology & Pharmacy; PHARMACOLOGY & PHARMACY; Research & Experimental Medicine

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