Characteristics of the Ca channel from pancreatic B-cells and its modulation by glucose

本文研究了电压依赖性钙通道对大鼠胰腺B细胞的葡萄糖调节作用。单通道电导为28ps，电流密度为55 mM，膜的外壁电导为28ps。为了排除葡萄糖代谢关闭ATP敏感性钾通道引起的膜电位变化对钙通道的影响，用高钾内液浴的方法将静息膜电位钳制在0 mV。当葡萄糖浓度增加2.8或5.6 mM至16.7 mM时，钙通道的开放概率增加2-3倍。在1亩M Bay K8644存在下，葡萄糖对通道的作用是一致的。开放时间直方图为单指数曲线，时间常数分别为0.2ms和0.29ms，葡萄糖浓度分别为5.6 mM和22.4 mM。分别进行了分析。闭合时间直方图需要两个时间常数，分别为0.82ms和18.9ms(5.6 mM葡萄糖)。22.4 mM葡萄糖时分别为0.91ms和5.05ms。这些结果提示，钙通道门控可能受葡萄糖代谢的调节。

Voltage-dependent Ca channels were studied with regard to glucose modulation in rat pancreatic B-cells. The single channel conductance was 28 pS at 55 mM Ba on the external side of the cell-attached patch membrane. In an effort to exclude the effects on the Ca channels of membrane potential changes due to closure of ATP-sensitive K channels by glucose metabolism, the resting membrane potential was chemically clamped at 0 mV by bathing the cell in the high K internal solution. The open-state probability of the Ca channels was increased 2-3 fold with an increase in glucose concentration for either 2.8 or 5.6 mM to 16.7 mM. Consistent effects of glucose on the channels were obtained in the presence of 1 mu M BAY K 8644. An open time histogram consisted of a single exponentia1 curve with a time constant of 0.2 ms and 0.29 ms at glucose concentration of 5.6 mM and 22.4 mM. respectively. Two time constants were required in the closed time histogram and they were 0.82 ms and 18.9 ms at 5.6 mM gucose. and 0.91 ms and 5.05 ms at 22.4 mM glucose. These results suggest that Ca-channel gating may be modulated by glucose metabolism.