Kitasato H
J Gen Physiol. 1968 Jul;52(1):60-87. doi: 10.1085/jgp.52.1.60.
The resting membrane potential of the Nitella cell is relatively insensitive to K, but behaves like a hydrogen electrode. K(+) and Cl(-) effluxes from the cell were measured continuously, while the membrane potential was changed either by means of a negative feedback circuit or by external pH changes. The experiments indicate that P(K) and P(Cl) are independent of pH but are a function of membrane potential. Slope ion conductances, G(K), G(Cl), and G(Na) were calculated from efflux measurements, and their sum was found to be negligible compared to membrane conductance. The possibility that a boundary potential change might be responsible for the membrane potential change was considered but was ruled out by the fact that the peak of the action potential remained at a constant level regardless of pH changes in the external solution. The conductance for H(+) was estimated by measuring the membrane current change during an external pH change while the membrane potential was clamped at K(+) equilibrium potential. In the range of external pH 5 to 6, H(+) chord conductance was substantially equal to the membrane conductance. However, the H measured by various methods was not such as would be predicted from the H and the membrane potential using the Nernst equation. In artificial pond water containing DNP, the resting membrane potential decreased; this suggested that some energy-consuming mechanism maintains the membrane potential at the resting level. It is probable that there is a H(+) extrusion mechanism in the Nitella cell, because the potential difference between the resting potential and the H(+) equilibrium potential is always maintained notwithstanding a continuous H(+) inward current which should result from the potential difference.
丽藻细胞的静息膜电位对K相对不敏感，但表现得像一个氢电极。在通过负反馈电路或外部pH变化改变膜电位的同时，持续测量细胞内K(+)和Cl(-)的外流。实验表明，P(K)和P(Cl)与pH无关，但却是膜电位的函数。根据外流测量计算出斜率离子电导G(K)、G(Cl)和G(Na)，发现它们的总和与膜电导相比可忽略不计。考虑了边界电位变化可能导致膜电位变化的可能性，但外部溶液pH变化时动作电位的峰值保持在恒定水平这一事实排除了这种可能性。通过在膜电位钳制在K(+)平衡电位时测量外部pH变化期间的膜电流变化来估计H(+)的电导。在外部pH 5至6的范围内，H(+)弦电导基本等于膜电导。然而，用各种方法测量的H并非使用能斯特方程根据H和膜电位预测的那样。在含有二硝基苯酚的人工池塘水中，静息膜电位降低；这表明某种耗能机制将膜电位维持在静息水平。丽藻细胞中可能存在H(+)外排机制，因为尽管由于电位差会持续有H(+)内向电流，但静息电位与H(+)平衡电位之间的电位差始终保持。
