Azide sensitive components of potassium efflux as influenced by the external sodium concentration

Summary Sodium azide at concentrations <–1.0 mM was capable of stimulating potassium efflux from frog sartorius muscles with no significant influence on the intracellular sodium content. At concentrations >–2.0 mM, azide produced a continuously increasing rate of potassium loss which resulted in a net loss of intracellular potassium. This effect was mimicked at low azide concentrations (<–1.0 mM) in the presence of 10^–5 M strophanthidin or 1.0 mM sodium cyanide. It was independent of the intracellular sodium content, but dependent on the external sodium concentration. While increasing concentrations of azide produced incremental increases in the rate of potassium loss in sodium-reduced Ringer's solution, the continuously increasing rate of loss and strophanthidin sensitivity was absent. It is concluded that the biphasic effect of azide on potassium efflux in skeletal muscle resulted from the interaction of this agent with at least two cellular processes, one of which was dependent on the external sodium concentration.