Kimitsuki T, Mitsuiye T, Noma A
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Am J Physiol. 1990 Jan;258(1 Pt 2):H247-54. doi: 10.1152/ajpheart.1990.258.1.H247.
Na+ channel kinetics were studied by recording single-channel currents in the cell-attached patch configuration of the patch-clamp technique in single ventricular cells isolated from guinea pig hearts. The inactivation time course of ensemble currents was accelerated, and the peak amplitude increased temporarily and then decreased within a few minutes after the gigaohm seal formation. After reaching a new steady state, the inactivation-voltage relation was found to have shifted to more negative potentials. The potential of half-maximal inactivation was more negative by 20-31 mV from the resting potential or between -96 and -112 mV. The voltage dependency of the channel activation also shifted. Although the cell membrane was depolarized using the whole cell patch-clamp electrode and single-channel currents were recorded with an independent cell-attached electrode, the shift of the inactivation curve was also evident. Complete removal of Ca2+ using 5 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid in the pipette solution failed to prevent the shift. Increasing Ca2+ to 10 mM, however, reduced magnitude of the shift significantly. Involvement of an increased membrane fluidity and surface potential of the glass pipette to the shift is discussed.
采用膜片钳技术的细胞贴附式膜片记录单个心室细胞的单通道电流，研究了Na⁺通道动力学。这些电流的失活时间进程加快，在形成千兆欧封接后的几分钟内，峰值幅度先暂时增加然后下降。达到新的稳定状态后，发现失活 - 电压关系已向更负的电位移动。半数最大失活电位比静息电位更负20 - 31 mV，或在 - 96至 - 112 mV之间。通道激活的电压依赖性也发生了变化。尽管使用全细胞膜片钳电极使细胞膜去极化，并使用独立的细胞贴附电极记录单通道电流，但失活曲线的移动也很明显。在移液管溶液中使用5 mM乙二醇 - 双（β - 氨基乙基醚） - N，N，N'，N' - 四乙酸完全去除Ca²⁺未能阻止这种移动。然而，将Ca²⁺增加到10 mM可显著降低移动幅度。讨论了膜流动性增加和玻璃移液管表面电位对这种移动的影响。
