The effect of inorganic phosphate on sodium fluxes in dog red blood cells.

The effect of extracellular inorganic phosphate on Na+ movements in dog red blood cells has been studied. As the phosphate concentration is increased from 0 to 30 mM, Na+ efflux increases by 2- to 3-fold and Na+ influx increases approximately 2-fold. This enhancement of Na+ fluxes by phosphate can be prevented by the addition of iodoacetate (1 mM), an inhibitor of glycolysis, or 4-acetamido-4'-iso-thiocyantostilbene-2,2'-disulfonic acid (0.01 mM), which blocks anion transport, to the medium. The increases in Na+ movements are not caused by changes in cell volumes. These results suggest that phosphate must enter the cell to enhance Na+ fluxes and that the mechanism of action may be via a stimulatory effect on glycolysis.