Na +- and anion-dependent Mg 2+ influx in isolated hepatocytes

Abstract

Hepatocytes, which were Mg 2+-depleted during isolation, took up Mg 2+ during reincubation. Mg 2+ uptake was dependent on the concentration of extracellular Mg 2+, Na +, Cl −, bicarbonate and phosphate, Li + and choline + did not substitute for extracellular Na + in Mg 2+ influx. Mg 2+ influx was maximal when all three anion species were present, and did not occur when these anions were replaced by gluconte. Bicarbonate, phosphate and Cl − could substitute for each other. Mg 2+ uptake in hepatocytes was inhibited by p- chloromercuribenzene sulfonate, ouabain, gramicidin D, amiloride and verapamil. The results were explained by the assumption that the net Mg 2+ influx in hepatocytes is operating via electroneutral Na +, Mg 2+/anion cotransport driven by the Na + gradient. However, electrogenic Mg 2+ uptake gated by extracellular Na + and anions could not be excluded.