Effect of adenosine triphosphate, magnesium, and calcium on the phosphate uptake by rabbit erythrocytes

Abstract

1. 1. The addition of adenosine triphosphate (ATP) to rabbit erythrocytes in vitro stimulated the uptake of labelled orthophosphate ions. 2. 2. The addition of calcium or magnesium ions alone inhibited phosphate uptake when the concentrations of Ca, Mg, and phosphate were approximately equal. 3. 3. The addition of both magnesium ions and ATP had a variable effect on phosphate uptake ranging from inhibition, when the concentrations of phosphate and magnesium were approximately equal, to stimulation when the concentration of ATP was greater or less than that of Mg. 4. 4. An attempt has been made to explain these observations on the basis of the known effects of ATP on the solubility of divalent alkaline metal phosphates and the possible interactions which might occur in a system including ATP, Mg and phosphate ions.