Sodium Extrusion in Muscle

Abstract

THE extrusion of sodium from the living cell against a concentration gradient has been demonstrated by Steinbach¹, Desmedt² and Maizels³. The mechanism of such an extrusion is often referred to as a ‘sodium pump’. We have repeated the above experiment with nerve and muscle; but we find it difficult to obtain consistent results, because toad (Bufo marinus) tissue does not always lose potassium and gain sodium in the cold. This pump is not entirely activated by temperature change, as the above authors neglect to stress that extrusion of sodium does not take place unless the external potassium is increased above physiological level.