The transfer of sodium ions between mammalian muscle and the surrounding medium

Abstract

The kinetics of loss of Na ions from mammalian muscle have been described. Following the rapid movement of the extracellular Na, the remainder is extruded with a uniform time constant of 1.59 h − at 20° C. Determination of the temperature coefficient for the process suggests that the rate-limiting step is a physical desorption of the ions. Na efflux is affected by the concentrations of both Na and K in the bathing solution, and K uptake by the muscles is conversely dependent on the presence of Na. The results suggest that the two processes are linked together in such a way that two Na ions are extruded for every K ion taken up.