Sodium and potassium movements in human red cells

Abstract

Radioactive tracers were used to study the movements of Na and K in washed human red cells suspended in buffered physiological salt solutions. Results suggest that K influx consists of a small passive component, proportional to the external K concentration, and a large active component depending on a mechanism which becomes saturated at high external K concentrations. Na efflux remains constant at ex ternal K concentrations greater than about 10 mM, but below 10 mM the efflux decreases. With no K outside, Na efflux is reduced by about 1/3 of its value at high K concentrations. Removal of glucose has no effect on Na efflux in the absence of K, but abolishes about 3/4 of the extra efflux which occurs in the presence of K. In a medium free from glucose and K, red cells do not show a net loss of Na when the external Na con centration is greater than the internal.