Hagiwara S, Ohmori H
J Physiol. 1983 Mar;336:649-61. doi: 10.1113/jphysiol.1983.sp014603.
Single Ca channel currents in tissue cultured clonal cells (GH3) isolated from a rat anterior pituitary tumour were studied with a patch voltage-clamp electrode filled with 100 mM-BaCl2 solution. The open time histogram was reasonably well expressed by a single exponential function with a time constant, which was about 1 msec and almost voltage-independent in the range of membrane potential studied (-20 to +40 mV). The closed time histogram was expressed by a sum of two exponential functions, one with a relatively voltage-independent time constant of about 1 msec and the other with a substantially larger voltage-dependent time constant. The latency (the time from the onset of the voltage-clamp pulse to the first channel opening) histogram could be expressed as the difference of two exponential functions with time constants which appeared to be voltage-dependent. The tentative conclusion is that the channel enters the activated state with voltage-dependent and relatively slow kinetics, and then flickers between open and closed states with substantially faster and relatively voltage-independent kinetics. The amplitude of the single channel current was similar to that estimated from noise analysis of the whole cell current (about -0.7 pA at 0 mV in 100 mM-BaCl2 solution); the apparent slope conductance was about 7-8 pS.
用充满100 mM氯化钡溶液的膜片电压钳电极研究了从大鼠垂体前叶肿瘤分离的组织培养克隆细胞（GH3）中的单个钙通道电流。开放时间直方图能用一个单指数函数较好地拟合，其时间常数约为1毫秒，在所研究的膜电位范围内（-20至+40 mV）几乎与电压无关。关闭时间直方图由两个指数函数之和表示，一个具有约1毫秒的相对电压无关的时间常数，另一个具有大得多的电压依赖性时间常数。潜伏期（从电压钳脉冲开始到第一个通道开放的时间）直方图可以表示为两个指数函数的差值，其时间常数似乎与电压有关。初步结论是，通道以电压依赖性和相对缓慢的动力学进入激活状态，然后以快得多且相对电压无关的动力学在开放和关闭状态之间闪烁。单通道电流的幅度与根据全细胞电流噪声分析估计的值相似（在100 mM氯化钡溶液中，0 mV时约为-0.7 pA）；表观斜率电导约为7 - 8 pS。
