Sadoshima J, Akaike N, Tomoike H, Kanaide H, Nakamura M
Research Institute of Angiocardiology and Cardiovascular Clinic, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Am J Physiol. 1988 Sep;255(3 Pt 2):H410-8. doi: 10.1152/ajpheart.1988.255.3.H410.
Electrical and pharmacological properties of the single Ca-activated K channel in cultured smooth muscle cells (SMC) of the rat aorta were studied with the patch-clamp technique. The Ca-activated K channel had a slope conductance (gamma K) of 135 +/- 2 pS (mean +/- SE; n = 5) in symmetrical 142 mM K solutions. The reversal potentials show a 56-mV change for a 10-fold change in the external K concentration. Probability of the channel opening increased when the intracellular Ca concentration ([Ca]i) was increased over 10(-7) M or the membrane was depolarized. The channel was blocked by either external tetraethylammonium (TEA, 10-30 mM) or by internal Ba (1-5 mM). Channel activities were characterized by burst-like openings. Open-time histogram was fitted with a single exponential (tau = 1.3 ms at +10 mV and 10(-7) M [Ca]i), whereas the closed-time histogram was fitted with two exponentials (tau 1 = 0.7 ms and tau 2 = 111 ms). The permeability ratio for monovalent cations calculated with the Goldman-Hodgkin-Katz equation was K:Rb:Na = 1:0.7: less than 0.01. We conclude from these observations that the Ca-activated K channel in cultured SMC of the rat aorta is characterized by a middle size gamma K, activation by [Ca]i increase and depolarization, relatively low sensitivity to TEA, and high selectivity for K ions.
采用膜片钳技术研究了大鼠主动脉培养平滑肌细胞（SMC）中单个钙激活钾通道的电学和药理学特性。在对称的142 mM钾溶液中，钙激活钾通道的斜率电导（γK）为135±2 pS（平均值±标准误；n = 5）。反转电位显示，细胞外钾浓度每变化10倍，电位变化56 mV。当细胞内钙浓度（[Ca]i）超过10^(-7) M或细胞膜去极化时，通道开放概率增加。该通道可被细胞外四乙铵（TEA，10 - 30 mM）或细胞内钡（1 - 5 mM）阻断。通道活动具有爆发样开放的特征。开放时间直方图拟合为单指数函数（在+10 mV和10^(-7) M [Ca]i时，τ = 1.3 ms），而关闭时间直方图拟合为双指数函数（τ1 = 0.7 ms和τ2 = 111 ms）。用戈德曼 - 霍奇金 - Katz方程计算的单价阳离子通透率比为K:Rb:Na = 1:0.7:小于0.01。我们从这些观察结果得出结论，大鼠主动脉培养SMC中的钙激活钾通道具有中等大小的γK、由[Ca]i增加和去极化激活、对TEA相对低敏感性以及对钾离子高选择性的特征。
