Nilius B, Kitamura K, Kuriyama H
K. U. Leuven, Labo Fysiologie, Belgium.
Pflugers Arch. 1994 Feb;426(3-4):239-46. doi: 10.1007/BF00374777.
With 10 mM Ba2+ as the charge carrier, inactivation of Ca2+ channel currents could be subdivided into at least two exponentials in smooth muscle cells dispersed from the rabbit portal vein by use of the whole-cell configuration of the patch-clamp technique: fast and slow inactivation. All characteristics of inactivation were independent of the size of the currents. Step changes in the holding potential unveiled an extremely slow recovery and an onset of inactivation of the order of several minutes. Steady-state inactivation critically depended on the duration of the pre-steps. Inactivation curves obtained under steady-state conditions showed as shift by approximately 25 mV towards negative potentials by comparison with curves obtained using 1-s pre-pulses. This shift greatly reduced the window current. Recovery from inactivation studied with double-pulse protocols could be classified into at least two exponentials. The contribution of the slow recovery was accentuated at negative holding potentials. Recovery from inactivation critically depended on the duration of the conditioning voltage step, and was also dependent on the duration of the pre-step: its voltage dependence disappeared when pre-pulses longer than 2 s were applied. Onset of inactivation was composed of at least two exponentials: the fast component was accelerated at less negative pre-step potentials. We propose that several inactivated states are involved in Ca2+ channel inactivation. Transitions between these states are voltage dependent and voltage independent.
以10 mM Ba2+作为电荷载体，利用膜片钳技术的全细胞模式，在从兔门静脉分离的平滑肌细胞中，Ca2+通道电流的失活可至少细分为两个指数过程：快速失活和缓慢失活。失活的所有特征均与电流大小无关。保持电位的阶跃变化揭示了极其缓慢的恢复以及数分钟量级的失活起始。稳态失活严重依赖于预脉冲的持续时间。与使用1秒预脉冲获得的曲线相比，稳态条件下获得的失活曲线向负电位方向偏移约25 mV。这种偏移极大地减小了窗口电流。用双脉冲方案研究的失活恢复可至少分为两个指数过程。在负的保持电位下，缓慢恢复的贡献更为突出。失活恢复严重依赖于条件电压阶跃的持续时间，并且还依赖于预脉冲的持续时间：当施加超过2秒的预脉冲时，其电压依赖性消失。失活起始至少由两个指数过程组成：快速成分在较不负的预脉冲电位下加速。我们提出，Ca2+通道失活涉及几种失活状态。这些状态之间的转变是电压依赖性和非电压依赖性的。
