Marom S, Salman H, Lyakhov V, Braun E
The Rappaport Faculty of Medicine and the Faculty of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.
J Membr Biol. 1996 Dec;154(3):267-74. doi: 10.1007/s002329900151.
The aim of this study is to evaluate directly, using a reduced experimental system, the nature of interactions between voltage-gated potassium channels and the resting membrane potential. Xenopus oocytes were injected with various concentrations of cRNA coding for a delayed-rectifier potassium channel Shaker-IR. The effects of the density and kinetics of the expressed channels on resting membrane potential is explored in isolated ("inside-out") patches. The channel density is given in terms of maximal conductance (Gmax), measured from the maximal slope of the I-V curve under voltage clamp conditions. The capacitance of the experimental setup is approximately 1 pF. At high channel densities (Gmax > 10 pA/mV) the mean membrane potential is stabilized at approximately -60 mV. This resting membrane potential is more than 35 mV positive to the reversal potential for potassium ions under the same experimental conditions. Analyses of voltage clamp experiments indicate that at high channel densities the mean membrane potential is determined by the rates of channel activation and deactivation, but is not affected by the rates involved in the process of slow (C-type) inactivation. In contrast, at lower channel densities membrane potential is very unstable, and its mean value and amplitude of fluctuations are strongly affected by the process of slow (C-type) inactivation.
本研究的目的是使用简化的实验系统直接评估电压门控钾通道与静息膜电位之间相互作用的性质。向非洲爪蟾卵母细胞注射编码延迟整流钾通道Shaker-IR的不同浓度的cRNA。在分离的（“内向外”）膜片中探究所表达通道的密度和动力学对静息膜电位的影响。通道密度以最大电导（Gmax）表示，其通过在电压钳制条件下从I-V曲线的最大斜率测量得出。实验装置的电容约为1 pF。在高通道密度（Gmax > 10 pA/mV）时，平均膜电位稳定在约 -60 mV。在相同实验条件下，该静息膜电位比钾离子的反转电位正超过35 mV。电压钳实验分析表明，在高通道密度时，平均膜电位由通道激活和失活的速率决定，但不受缓慢（C型）失活过程中涉及的速率影响。相反，在较低通道密度时，膜电位非常不稳定，其平均值和波动幅度受到缓慢（C型）失活过程的强烈影响。
