Effect of some monovalent anions on chloride and sulphate permeability of human red cells

Abstract

1. The permeability of human red cells to (36)Cl(-) and to [(35)S]SO(4) (2-) was studied in the presence of various monovalent anions.2. A maximum decrease of anion permeability was found in a study of the steady-state exchange of (36)Cl in a medium containing 120 mM salicylate. The exchange had a half-time of 3 hr at 0 degrees C, a reduction of normal chloride permeability by a factor of 10(5). The activation energy of chloride exchange decreased from a value of 45 to 22 kcal/mole in the interval between 0 and 10 degrees C. Simultaneous determination of the permeability to potassium and chloride proved that salicylate induced a reversal of the normal selectivity of red cells at 0 degrees C (permeability coefficient P(K) of 3.5 x 10(-9) cm/sec to be compared with a P(Cl) of 2 x 10(-9) cm/sec).3. In contradistinction to the slow movement of (36)Cl, the exchange of [(14)C]salicylate was completed within 4 min, when red cells were suspended at 0 degrees C in the salicylate medium.4. A study of the sulphate permeability at 38 degrees C showed that the rate of steady-state exchange decreased, when chloride was replaced by lyotropic anions other than bromide. The sequence of the permeability decrease was: Cl(-) = Br(-) < I(-) < NO(3) < SCN(-) < salicylate, the same sequence which previously has been shown to increase the permeability to sodium and potassium. The activation energies of sulphate exchange were 32 kcal/mole (chloride medium), and 38 kcal/mole (thiocyanate medium).5. Sufficient data were obtained during the study to demonstrate that when equilibrium has been obtained, there is a good agreement between the values of (36)Cl (cell water)/(36)Cl (extracellular water) and of {[(35)S]SO(4) (cell water)/[(35)S]SO(4) (extracellular water)}((1/2)).6. It is concluded that the anion-induced changes of permeability are due to binding of anions to fixed cationic charges in the red cell membrane.