Evidence for a differential cellular distribution of inward rectifier K channels in the rat isolated mesenteric artery.
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.
Crane
G J
GJ
Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, UK.
Walker
S D
SD
Dora
K A
KA
Garland
C J
CJ
D000818:Animals; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008638:Mesenteric Arteries / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D010042:Ouabain