The relation between net calcium, alkali cation and chloride movements in red cells exposed to salicylate.

1. From a 150 mM‐NH4 salicylate medium salicylate enters human red cells with a rate constant of 1.9 min‐1 at 0 degrees C. 2. Salicylate increases the red cell permeability for Ca2+ (and Mg2+). There is no saturation of the Ca2+ transfer with respect to salicylate up to 150 mM and with respect to external Ca2+ up to 30 mM. 3. Ca2+ entering from salicylate media activates the Ca‐sensitive K channel present in human but not in adult ruminant red cells. 4. The increase in K permeability which ensues hyperpolarizes the membrane in Na salicylate media, accelerating further Ca2+ entry and Mg2+ entry and favouring Cl‐ loss (see Fig. 8). The Ca2+ inward movement is in agreement with the constant field equation if the membrane potential is assumed to equal the K equilibrium potential and if two charges are attributed to the mobile species. 5. The effect of salicylate on Ca2+ permeability and hence its sequelae are reversible upon washing the cells. 6. 3‐OH‐benzoic acid and 4‐OH‐benzoic acid do not exert the effect salicylate has on Ca2+ permeability. 7. In 150 mM‐Na salicylate media the Cl‐‐salicylate exchange is virtually nil at 0 degrees C. The exchange seen at 19 degrees C is obviously not across the anion exchange mechanism and proceeds at a rate comparable to that for Cl‐ movement in the nonexchange‐restricted mode given by Hunter (1971, 1977) for cells in a normal medium. 8. Ca2+ seems to increase the Cl‐ permeability seen under these conditions. 9. The possibility that salicylate acts as an ionophore for Ca2+ is discussed.