ATP-dependent closure and reactivation of inward rectifier K+ channels in endothelial cells.

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Abstract
This report presents the results of a patch-clamp study examining the role of intracellular ATP in the regulation of endothelial inward rectifier K+ channels. Administration of ATP to the cytosolic surface of inside-out patches reversibly activated the K+ channel within seconds. ATP (1 mM) increased the mean open probability by a factor of 3.5, primarily by increasing the number of openings. Administration of the nonhydrolyzable ATP analogue ATP-gamma-S failed to modulate channel activity. Inhibition of ATP synthesis by administration of cyanide plus iodoacetate resulted in channel closure within 1 to 6 minutes. In experiments in which ATP was coadministered with the metabolic blockers, the channel activity continued unchanged for up to 30 minutes, but when ATP was removed, the activity rapidly decayed. We propose that normal functioning of the inward rectifier K+ channel is ATP dependent. Phosphorylation of the channel molecule is probably essential for maintaining activity.