Takano M, Qin D Y, Noma A
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Am J Physiol. 1990 Jan;258(1 Pt 2):H45-50. doi: 10.1152/ajpheart.1990.258.1.H45.
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.
利用心肌细胞的内向外膜片钳记录技术，研究了内向整流钾通道和ATP敏感性钾通道的ATP依赖性衰减和恢复过程。采用油门浓度阶跃法瞬间改变面向膜内侧的溶液。去除ATP时，两种通道均发生衰减，重新加入ATP后恢复。恢复过程需要Mg2+的共存。5'-腺苷酰亚胺二磷酸不能逆转ATP依赖性衰减。从内向整流钾通道获得的存活时间和恢复时间的累积直方图显示为单指数分布，其时间常数分别为55秒和43秒。ATP敏感性钾通道的衰减和恢复的时间依赖性也得到了证实。这些发现表明，细胞内ATP是决定钾通道活性的因素之一。通道分子的磷酸化很可能是使钾通道维持在可操作状态所必需的。
