人脐血红细胞膜的钙激活钾通道

CA^(2+)-ACTIVATED K^+ CHANNELS IN RED CELLS OF HUMAN CORD BLOOD

作者应用膜片钳技术研究了人脐血红细胞电压依赖和钙活钾通道的电学特性。在细胞吸附膜片中，对称性140mM钾溶液条件下，该通道有一个28．6pS的斜率电导，同时表现出高度K＋选择性．实验发现通道对细胞内钙敏感，当膜电位变正或胞内Ca2＋从10－6M升高到10－5M时，通道开放的频率与时间增加。胞外应用TEA10mM能有效阻断通过电流。从该通道表现出的小电导、能被膜去极化和胞内Ca2＋升高所激活，能被TEA阻断和对K＋高度选择性这样一些特点，我们得出结论，这个通道类似于在其它不同组织上发现的钙激活钾通道．

The electrical properties of the voltage dependent and Ca2＋-activated K＋channel were studied with the patch clamp technique on red cells of human cord blood. The channel which had a slope conductance of 28. 6 pS under symmetrical 140 mM K＋ solution in cell-attached patch was shown to be highly K＋ selective, This channel was found to be sensitive to [Ca2＋] i. The frequency and duration of the channel opening increased when the intracellular Ca2＋ conoentration was increased from 10-6to 10-5M and/or when the membrane potential was made more positive. External tetraethylammonium (TEA, 10mM ) was effective in blocking the channel currents. We conclude from these observations that the Ca2＋-activated K+ channels in red cells of human cord blood are characteriaed by small conductance, activation by [Ca2＋] i increase and membrane depolarization , blocking by TEA, and high selectivity for K＋ ions. Thus, the features of this channel resemble the Ca2＋-activated K+ channel found in a wide variety of other tissues.