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The distribution of functionally active, inwardly rectifying K (K(IR)) channels was investigated in the rat small mesenteric artery using both freshly isolated smooth muscle and endothelial cells and small arterial segments. In Ca(2+)-free solution, endothelial cells displayed a K(IR) current with a maximum amplitude of 190 +/- 16 pA at -150 mV and sensitivity to block with 30 microM Ba(2+) (n = 7). In smooth muscle cells, outward K current was activated at around -47 +/- 3 mV, but there was no evidence of K(IR) current (n = 6). Furthermore, raising extracellular [K(+)] to either 60 or 140 mM, or applying the alpha(1)-adrenoceptor agonist phenylephrine (PE; 30 microM), failed to reveal an inwardly rectifying current in the smooth muscle cells, although PE did stimulate an iberiotoxin-sensitive outward K current (n = 4). Exogenous K(+) (10.8-16.8 mM) both relaxed and repolarized endothelium-denuded segments of the mesenteric artery contracted with PE. These effects were depressed by 100 microM ouabain but unaffected by either 30 microM BaCl(2) or 3 microM glibenclamide. These data suggest that functional, inwardly rectifying Ba(2+)-sensitive channels are restricted to the endothelial cell layer in the rat small mesenteric artery.

Type

Journal article

Journal

J Vasc Res

Publication Date

03/2003

Volume

40

Pages

159 - 168

Keywords

Animals, Endothelium, Vascular, Enzyme Inhibitors, In Vitro Techniques, Male, Membrane Potentials, Mesenteric Arteries, Muscle Contraction, Muscle, Smooth, Vascular, Ouabain, Patch-Clamp Techniques, Potassium Channel Blockers, Potassium Channels, Inwardly Rectifying, Rats, Rats, Wistar, Vasodilation