Muscarinic-activated K+ current in bovine aortic endothelial cells.

Isolated, cultured arterial endothelial cells express an acetylcholine (ACh)-activated K+ current in addition to an inward rectifier current whose conductance is unaffected by ACh. The cholinergic K+ current is specifically blocked by atropine (1 microM) and shows single saturation kinetics with ACh (half-maximal stimulation 51 nM ACh). Unlike the cardiac muscarinic receptor-gated K+ channel, its stimulation appears independent of a pertussis toxin-sensitive GTP-binding protein. Activation of the endothelial muscarinic K+ current resulting in hyperpolarization may represent an initial component of the vasodilatory effect of ACh.