The transport of phosphate ions across the human red cell membrane

1.1. The concentrations of chloride and phosphate ions in the cellular and extracellular phases have been determined in suspensions of human red cells incubated for about 3 h in salt solutions containing various concentrations of chloride and phosphate ions.2.2. The concentration ratio of primary phosphate ions between the cellular and extracellular phases was in all cases found to be related to that of the chloride ions by a constant factor.3.3. The significance of this result and its possible consequences for the problem of the mechanism of the transport of phosphate ions across the human erythrocyte membrane are discussed.