Evidence for a carrier-mediated exchange-diffusion entry of calcium into erythrocytes

The enthalpy of activation of entry of 45Ca into erythrocytes under conditions of zero net transport (19 Kcal/mol), inhibition of entry by N-ethylmaleimide, and transport pH optimum of 7 - 7.5 are consistent with a protein carrier for inward calcium movement. Initial rate analysis shows saturation kinetics and transstimulation, consistent with a carrier-mediated exchange-diffusion mechanism.