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

电压依赖性钙通道进行了研究，在大鼠胰腺B细胞的葡萄糖调制。单通道电导为28 pS，在55 mM Ba的细胞附着的补丁膜的外侧。为了排除由于葡萄糖代谢导致ATP敏感性K通道关闭而引起的膜电位变化对Ca通道的影响，通过将细胞浸泡在高K内溶液中，将静息膜电位化学钳位在0 mV。钙通道的开放状态的概率增加2-3倍，在葡萄糖浓度的增加，无论是2.8或5.6 mM至16.7 mM。一致的影响，葡萄糖对通道的1 μ M BAY K 8644的存在下获得。开放时间直方图由单指数曲线组成，在葡萄糖浓度分别为5.6 mM和22.4 mM时，时间常数为0.2 ms和0.29 ms。在闭合时间直方图中需要两个时间常数，在5.6 mM葡萄糖下为0.82 ms和18.9 ms。在22.4mM葡萄糖下分别为0.91 ms和5.05 ms。这些结果表明，钙通道门控可能是由葡萄糖代谢调制。

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.