Characterization of Na(+)-dependent Mg2+ efflux from Mg2(+)-loaded rat erythrocytes.

Abstract

Na(+)-dependent Mg2+ efflux from Mg2(+)-loaded rat erythrocytes was determined from the increase of extracellular Mg2+ concentration or decrease of intracellular Mg2+ content, as measured by means of atomic absorption spectrophotometry. Mg2+ efflux was specifically combined with the uptake of Na+ at a stoichiometric ratio of 2Na+:1Mg2+, indicating electroneutral Na+/Mg2+ antiport. Na+/Mg2+ antiport depended on intracellular ATP and was inhibited by amiloride and quinidine, but was insensitive to strophanthin. Net Mg2+ efflux was only occurring at increased concentration of intracellular Mg2+ ([Mg2+]i), and stopped when the physiological Mg2+ content was reached. Intracellular Mg2+ acted cooperatively with a Hill coefficient of 2.4, which may indicate gating of Na+/Mg2+ antiport at increased [Mg2+]i. At increased intracellular Na+ concentration, Na+ competed with intracellular Mg2+ for Mg2+ efflux and Na+ could leave the rat erythrocyte via this transport system. Na+/Mg2+ antiport was working asymmetrically with respect to extra- and intracellular Na+ and Mg2+, and did not perform net Mg2+ uptake.

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@article{Gnther1990CharacterizationON, title={Characterization of Na(+)-dependent Mg2+ efflux from Mg2(+)-loaded rat erythrocytes.}, author={Theodor G{\"{u}nther and Juergen Vormann and Vera H{\"{o}llriegl}, journal={Biochimica et biophysica acta}, year={1990}, volume={1023 3}, pages={455-61} }