Ruiz-Ceretti E, Nguyen T A, Schanne O F, Caille J P
Am J Physiol. 1981 Jan;240(1):C28-34. doi: 10.1152/ajpcell.1981.240.1.C28.
The resting potential and the intracellular Na and K concentrations (Nai, Ki) were determined at several extracellular K concentrations (Ko) between 0.5 and 18 mM and after inhibition of the sodium pump with 0.5 microM ouabain. Exposure to low Ko (0.5 mM) produced a transient hyperpolarization (from -80 to -100 mV) followed by a depolarization that led to a stable potential of -60 mV within 25 min. Similar potential levels were observed in the presence of ouabain regardless of the Ko/Ki ratio. Intracellular sodium increased at Ko < 5 mM, whereas Ki rose at Ko less than or equal to 1.0 mM. Because of the large decrease of Ki at Ko = 0.5 mM, Ko/Ki was the same at 0.5 and 1 mM. However, the resting potentials at the steady state differed by 50 mV at these concentrations. A PNa/PK of 0.032 for the control conditions was obtained with the Mullins-Noda equation using 2.5 as the Na-K coupling ratio. This PNa/PK value yielded a Goldman potential of -69 mV; so we estimated that electrogenic sodium extrusion contributed -10 mV to the resting potential. The size of the electrogenic potential increased as Ko was lowered from 5 to 1 mM. This finding suggests that the control of the Na-K coupling ratio may be independent of the mechanism that controls the pumping rate.
在0.5至18 mM的几种细胞外钾浓度（Ko）下，以及在用0.5 microM哇巴因抑制钠泵后，测定静息电位和细胞内钠钾浓度（Nai、Ki）。暴露于低钾（0.5 mM）会产生短暂的超极化（从-80 mV至-100 mV），随后是去极化，导致在25分钟内达到稳定电位-60 mV。无论Ko/Ki比值如何，在哇巴因存在的情况下观察到类似的电位水平。当Ko < 5 mM时，细胞内钠增加，而当Ko小于或等于1.0 mM时，Ki升高。由于在Ko = 0.5 mM时Ki大幅下降，Ko/Ki在0.5和1 mM时相同。然而，在这些浓度下，稳态时的静息电位相差50 mV。在对照条件下，使用2.5作为钠钾耦合比，通过穆林斯-野田方程获得PNa/PK为0.032。该PNa/PK值产生的戈德曼电位为-69 mV；因此我们估计电生性钠排出对静息电位贡献了-10 mV。随着Ko从5 mM降至1 mM，电生性电位的大小增加。这一发现表明，钠钾耦合比的控制可能独立于控制泵浦速率的机制。
