Stutzin A, Stojilković S S, Catt K J, Rojas E
Laboratory of Cell Biology and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Am J Physiol. 1989 Nov;257(5 Pt 1):C865-74. doi: 10.1152/ajpcell.1989.257.5.C865.
The properties of Ca2+ channels in cultured rat pituitary gonadotrophs were analyzed by the patch-clamp technique. The inward Ca2+ currents, recorded in the presence of 5.2 mM Ca2+ or Ba2+, included a fast, transient component with activation-inactivation kinetics and a delayed component with slower activation. The midpoint of the activation curve lay at -30 mV for the transient component and at -12 mV for the delayed component. At the midpoint, changes in potential of 9.5 and 13 mV induced an e-fold change in the activation of the transient and delayed components, respectively. The rate of inactivation of the first component was strongly voltage dependent. At -43 mV, a 7.4-mV change in potential induced an e-fold change in the fraction of Ca2+ channels available to conduct Ca2+ current. During long-lasting (100-200 ms) low-frequency depolarizing voltage-clamp pulses, the size of the delayed component of the Ca2+ current remained constant. The differential effects of membrane potential on inactivation and the different time constants for activation of the two components of the Ca2+ conductance indicate the presence of two types of Ca2+ channels in the membrane of the gonadotroph: the rapidly inactivating current appears to be attributable to a T-type channel, and the noninactivating current corresponds to the L-type channel described in many other cell types.
采用膜片钳技术分析了培养的大鼠垂体促性腺细胞中Ca2+通道的特性。在存在5.2 mM Ca2+或Ba2+的情况下记录到的内向Ca2+电流包括一个具有激活-失活动力学的快速瞬态成分和一个激活较慢的延迟成分。瞬态成分的激活曲线中点位于-30 mV，延迟成分的激活曲线中点位于-12 mV。在中点处，9.5 mV和13 mV的电位变化分别引起瞬态和延迟成分激活的e倍变化。第一个成分的失活速率强烈依赖于电压。在-43 mV时，7.4 mV的电位变化引起可传导Ca2+电流的Ca2+通道分数的e倍变化。在长时间（100 - 200 ms）低频去极化电压钳脉冲期间，Ca2+电流延迟成分的大小保持恒定。膜电位对失活的不同影响以及Ca2+电导两个成分激活的不同时间常数表明促性腺细胞膜中存在两种类型的Ca2+通道：快速失活电流似乎归因于T型通道，非失活电流对应于许多其他细胞类型中描述的L型通道。
