Stimulation of Na+/Mg2+ antiport in rat erythrocytes by intracellular Cl−

[摘要]

Mg²⁺ efflux from rat erythrocytes was measured in NaCl, NaNO₃, NaSCN and Na gluconate medium. Substitution of extracellular and intracellular Cl⁻ with the permeant anions NO₃ ⁻ and SCN⁻ reduced Mg²⁺ efflux via Na⁺/Mg²⁺ antiport. After substitution of extracellular Cl⁻ with the non-permeant anion gluconate, Mg²⁺ efflux was not significantly reduced. In Na gluconate medium, an influence of the changed membrane potential and intracellular pH on Mg²⁺ efflux could be excluded. The results indicate the existence of Cl⁻-independent Na⁺/Mg²⁺ antiport and of Na⁺/Mg²⁺ antiport stimulated by intracellular Cl⁻. Intracellular Cl⁻, as determined by means of ³⁶Cl⁻, was found to stimulate Na⁺/Mg²⁺ antiport through a cooperative effect according to a sigmoidal kinetics. The Hill coefficient for intracellular Cl⁻ amounted to 1.4–1.8, indicating that two intracellular Cl⁻ may be simultaneously active. With respect to specificity, Cl⁻ was most effective, followed by Br⁻, J⁻, and F⁻. Stimulation of Na⁺/Mg²⁺ antiport by intracellular Cl⁻ together with intracellular Mg²⁺ may play a role during deoxygenation of erythrocytes and in essential hypertension.

[学科分类] 生物化学/生物物理

[关键词] Na+/Mg2+ antiport;[Cl−]i stimulation;Deoxygenation;Essential hypertension;Rat erythrocyte