Characterization of ATP-sensitive potassium channels in freshly dissociated rabbit aortic endothelial cells

ATP-sensitive potassium (K-ATP) 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 presence of an K-ATP conductance has recently been demonstrated in freshly dissociated endothelial cells from rabbit arteries. In the present study, the single-channel activity underlying the K-ATP 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 similar to 150 and similar to 25 pS that were inhibited by either 6 mM ATP or 10 mu M glibenclamide. A small conductance channel was also activated in cell-attached patches by bath-applied levcromakalim (25 mu M) Activation of endothelial cell K-ATP 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.