上皮细胞基底外侧膜上的钠钾转运。III. 基底外侧膜钠外流的电压独立性
Na+ and K+ transport at basolateral membranes of epithelial cells. III. Voltage independence of basolateral membrane Na+ efflux.
作者信息
Cox T C, Helman S I
出版信息
J Gen Physiol. 1986 Mar;87(3):503-9. doi: 10.1085/jgp.87.3.503.
Na+ efflux across basolateral membranes of isolated epithelia of frog skin was tested for voltage sensitivity. The intracellular Na+ transport pool was loaded with 24Na from the apical solution and the rate of isotope appearance in the basolateral solution (JNa23) was measured at timed intervals of 30 s. Basolateral membrane voltage was depolarized by either 50 mM K+, 5 mM Ba++, or 80 mM NH+4. Whereas within 30 s ouabain caused inhibition of JNa23, depolarization of Vb by 30-60 mV caused no significant change of JNa23. Thus, both pump-mediated and leak Na+ effluxes were voltage independent. Although the pumps are electrogenic, pump-mediated Na+ efflux is voltage independent, perhaps because of a nonlinear relationship between pump current and transmembrane voltage. Voltage independence of the leak Na+ efflux confirms a previous suggestion (Cox and Helman, 1983. American Journal of Physiology. 245:F312-F321) that basolateral membrane Na+ leak fluxes are electroneutral.
对蛙皮离体上皮细胞基底外侧膜上的Na⁺外流进行了电压敏感性测试。从顶端溶液中用²⁴Na加载细胞内Na⁺转运池，并在30秒的时间间隔内测量基底外侧溶液中同位素出现的速率（JNa²³）。通过50 mM K⁺、5 mM Ba²⁺或80 mM NH₄⁺使基底外侧膜电压去极化。虽然哇巴因在30秒内导致JNa²³受到抑制，但将Vb去极化30 - 60 mV并未引起JNa²³的显著变化。因此，泵介导的和漏出的Na⁺外流均不依赖电压。尽管泵是生电的，但泵介导的Na⁺外流不依赖电压，这可能是由于泵电流与跨膜电压之间存在非线性关系。漏出的Na⁺外流不依赖电压证实了之前的一个观点（考克斯和赫尔曼，1983年。《美国生理学杂志》。245:F312 - F321），即基底外侧膜Na⁺漏出通量是电中性的。
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