Takahashi A, Yamaguchi H, Miyamoto H
Department of Physiology, School of Medicine, University of Tokushima, Japan.
Am J Physiol. 1993 Aug;265(2 Pt 1):C328-36. doi: 10.1152/ajpcell.1993.265.2.C328.
The K+ channel of HeLa S3 cells in metaphase was analyzed by inside-out and whole cell patch-clamp techniques. The channel had the characteristics of strong inward rectification, small conductance (22 pS at -100 mV), and dependence on intracellular Ca2+. We investigated the cell cycle dependency of the channel, using cells synchronized by harvesting them at the mitotic stage. The cell capacitance increased gradually with increases in the cell volume toward the S phase. The inward K+ currents through the channel at fixed membrane potentials were highest in early G1 and then decreased with time to a minimum in the S phase, increasing again in the M phase. The permeabilities at fixed membrane potentials were also highest in early G1, decreased to minima in the S phase, and increased again toward the next mitosis. In contrast, mean amplitude and the open probability of the single channel at a fixed membrane potential (-60 mV) did not change significantly during the cell cycle. Therefore the capacitance increases with progression of the cell cycle, whereas the permeability decreases from early G1 to an apparent minimum in the S phase. These changes may be caused by cell cycle-dependent changes in the number of channels.
采用内面向外式和全细胞式膜片钳技术分析了中期HeLa S3细胞的钾离子通道。该通道具有强内向整流、小电导（在-100 mV时为22 pS）以及依赖细胞内钙离子的特性。我们使用在有丝分裂期收获的同步化细胞研究了该通道的细胞周期依赖性。细胞电容随着细胞体积向S期增加而逐渐增大。在固定膜电位下通过该通道的内向钾离子电流在G1早期最高，然后随时间下降至S期的最小值，在M期又再次增加。在固定膜电位下的通透性在G1早期也最高，在S期降至最小值，并在下一次有丝分裂时再次增加。相比之下，在固定膜电位（-60 mV）下单个通道的平均幅度和开放概率在细胞周期中没有显著变化。因此，电容随着细胞周期的进展而增加，而通透性从G1早期到S期明显最小值逐渐降低。这些变化可能是由通道数量的细胞周期依赖性变化引起的。
