AJP - Heart and Circulatory Physiology, Vol 258, Issue 1 45-H50, Copyright © 1990 by American Physiological Society

ARTICLES

ATP-dependent decay and recovery of K+ channels in guinea pig cardiac myocytes

M. Takano, D. Y. Qin and A. Noma
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.

ATP-dependent decay and recovery of the inward rectifier and ATP-sensitive K+ channels were investigated using inside-out patch recording in cardiac myocytes. The solution facing the inner side of the membrane was instantaneously changed with the oil-gate concentration jump method. Both channels were decayed by removing ATP and were recovered by reapplying ATP. The coexistence of Mg2+ was required for the recovery. 5'-Adenylylimidodiphosphate failed to reverse the ATP-dependent decay. The cumulative histograms of survival time and recovery time, obtained from the inward rectifier K+ channel, showed a single exponential distribution, time constants of which were 55 and 43 s, respectively. The time-dependent nature of decay and recovery was also confirmed in the ATP-sensitive K+ channel. The findings indicated that intracellular ATP is one of the factors that determines the activity of the K+ channels. It is most probable that phosphorylation of channel molecules is essential for maintaining the K+ channel in an operative state.

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