Search for a Potassium Compartment in the Human Red Cell Membrane

Abstract

THE present experiments are concerned with the search for a potassium carrier in the membrane of the human red cell. From studies on the efflux of potassium-42 from human red cells, Solomon and Gold¹ concluded that the cell contained its intracellular potassium in two separate compartments. The larger compartment was assumed to contain 41.6 m.eq. potassium/l. blood; the smaller compartment was assumed to contain 1.75 m.eq. potassium/l. blood², and to reach its peak specific activity about 1.5 hr. after potassium-42 was added to the system. Fig. 1 shows an analogue computer curve giving the time course of the predicted relative specific activities of the three compartments under the present experimental conditions. In order to determine whether the smaller compartment could be identified with the membrane phase, the kinetics of the uptake of potassium-42 by the cellular membrane have been studied over the time period of a few minutes to six hours. They have failed to reveal the presence of a significant potassium-containing compartment within the membrane phase. Since the time resolution of the present experiments is about three minutes, no information is available about processes which may be complete in shorter times.