Brodie C, Sampson S R
Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
Int J Dev Neurosci. 1989;7(2):165-72. doi: 10.1016/0736-5748(89)90066-x.
The role of the electrogenic Na+-K+ pump in the determination of the level of the resting membrane potential in cultured chick limb muscle was investigated. Transmembrane resting potential and ouabain-sensitive 86Rb-uptake were measured in myotubes at different ages in culture from 2 to 10 days in vitro. Inhibition of the Na+-K+ pump with ouabain prevented the developmental increase in membrane potential which normally follows fusion of myotubes (day 2-3). In mature myotubes, ouabain caused a dose-related decrease in both membrane potential and 86Rb-uptake, with values for EC50 and maximal effect being nearly the same on both variables. The decrease in membrane potential by ouabain, up to 20 mV maximum, occurred within 2-5 sec and was not accompanied by detectable changes in input resistance. Membrane potential was also reduced by a decrease in temperature of the recording medium and removal of extracellular K+, both of which reduce Na+-K+ pump activity. We also found that the relation between membrane potential and extracellular K+ concentration was completely attenuated by ouabain in the physiological range (2-10 mM). We conclude that the electrogenic Na+-K+ pump plays an important role in the determination of the resting membrane potential of chick myotubes and that regulation of its level is not entirely explained by the diffusion potential hypothesis.
研究了生电钠钾泵在培养的鸡胚肢体肌肉静息膜电位水平测定中的作用。在体外培养2至10天的不同年龄的肌管中测量跨膜静息电位和哇巴因敏感的86Rb摄取。用哇巴因抑制钠钾泵可阻止肌管融合（第2 - 3天）后膜电位的正常发育性增加。在成熟肌管中，哇巴因导致膜电位和86Rb摄取均呈剂量依赖性下降，两者的EC50值和最大效应值几乎相同。哇巴因使膜电位下降，最大可达20 mV，在2 - 5秒内发生，且输入电阻无明显变化。记录介质温度降低和细胞外钾去除也会降低膜电位，这两者都会降低钠钾泵活性。我们还发现，在生理范围内（2 - 10 mM），哇巴因可完全减弱膜电位与细胞外钾浓度之间的关系。我们得出结论，生电钠钾泵在鸡胚肌管静息膜电位的测定中起重要作用，其水平的调节不能完全用扩散电位假说来解释。
