AJP - Cell Physiology, Vol 237, Issue 1 96-101, Copyright © 1979 by American Physiological Society
Calcium transport in human red blood cells under hypertonic conditions
G. A. Plishker and H. J. Gitelman
Calcium accumulation in intact human erythrocytes is enhanced by incubation
in hypertonic solutions. Hypertonicity produces an increased permeability
of the membrane to calcium that is time-dependent and occurs in the
presence or absence of calcium. When hypertonically treated cells are
incubated for more than 30 min in 300 mosmol/kg solutions the permeability
of the membrane to calcium returns to basal values. Oligomycin inhibits the
effect of hypertonicity on calcium uptake. The inhibitory action of
oligomycin diminishes as the external sodium increases and can only be
observed when the external concentration of potassium is at or below 3 mM.
Low intracellular sodium and high intracellular potassium concentrations
increase the uptake of calcium. It is concluded for human erythrocytes that
1) the increased permeability of the membrane to calcium produced by
hypertonicity is a time-dependent, reversible phenomenon and is independent
of calcium, 2) the increase in intracellular potassium concentration
associated with hypertonic exposure is an important factor contributing to
this response, and 3) interactions between calcium and components of the
sodium-potassium transport system may account for the enhanced uptake of
calcium produced by hypertonicity.
