Characterization of ATP-sensitive potassium channels in freshly dissociated rabbit aortic endothelial cells
ATP-sensitive potassium (KATp) channels represent a class of K+ channel regulated by intracellular ATP and serve to transduce changes in cell metabolism into changes in membrane potential. The prèsence of an KATP conductance has recently been demonstrated in freshly dissociated endothelial cells from rabbit arteries. Iri the present study, the single-channel activity underlying the KATP conductance in rabbit aortic endothelial cells was examined. Unitary currents were evoked in response to lowering intracellular ATP concentration or application of the K+channel activator levcromakalim and were inhibited by the sulfonylurea drug glibenclamide. Exposure of the cytoplasmic face of an inside-out membrane patch to a solution containing 0.1 mM ATP produced single-channel events with unitary conductances of -150 and -25 pS that were inhibited by either 6 mM ATP or 10 μM glibenclamide. A small conductance channel was also activated in cell-attached patches by bath-applied levcromakalim (25 fiM). Activation of endothelial cell KATP channels, and subsequent membrane hyperpolarization, may contribute to endothelium-dependent regulation of vascular smooth muscle tone in response to changes in levels of intracellular metabolites.