Seabrooke S R, Ward M R, White N K
Department of Physiology, University of Dundee.
Q J Exp Physiol. 1988 Jul;73(4):561-72. doi: 10.1113/expphysiol.1988.sp003176.
The Na+ pump inhibitor ouabain produced a 25 mV depolarization of mouse extensor digitorum longus muscle fibres in 2 h. Approximately 40% of this depolarization could be prevented by the inclusion of tetrodotoxin (TTX) in the incubation fluid, and the membrane potential of ouabain-depolarized fibres increased when external Na+ ion concentration was reduced. TTX and Na+ reduction were without effect on fibres incubated for 2 h in the control saline or on fibres depolarized by raising external K+ ion concentration. Ouabain induced a fall in input resistance in fibres of reduced chloride conductance. Part of the depolarization induced in the majority of fibres by K+-free solutions was also TTX sensitive. These results suggest that the steady-state Na+ permeability of muscle fibres is increased after Na+ pump blockade. The ouabain-induced depolarization of skeletal muscle therefore cannot be taken as evidence for a significant contribution of an electrogenic Na+ pump to the resting membrane potential. TTX also reverses much of the depolarization which occurs after denervation of skeletal muscle. Denervation and ouabain both increase the steady-state Na+ permeability of the sarcolemma, possibly by an action on the same population of Na+ channels.
钠泵抑制剂哇巴因在2小时内使小鼠趾长伸肌纤维发生了25毫伏的去极化。在孵育液中加入河豚毒素（TTX）可阻止约40%的这种去极化，并且当细胞外钠离子浓度降低时，哇巴因去极化纤维的膜电位会升高。TTX和降低钠离子浓度对在对照盐溶液中孵育2小时的纤维或因提高细胞外钾离子浓度而发生去极化的纤维没有影响。哇巴因使氯离子电导降低的纤维的输入电阻下降。无钾溶液在大多数纤维中诱导的部分去极化也对TTX敏感。这些结果表明，钠泵被阻断后，肌纤维的稳态钠通透性增加。因此，哇巴因诱导的骨骼肌去极化不能被视为电生性钠泵对静息膜电位有显著贡献的证据。TTX也能逆转骨骼肌去神经支配后发生的大部分去极化。去神经支配和哇巴因都可能通过作用于同一群钠通道而增加肌膜的稳态钠通透性。
