Hormone-stimulated Mg2+ accumulation into rat hepatocytes: a pathway for rapid Mg2+ and Ca2+ redistribution

Many diseases such as cardiac arrhythmia, diabetes, and chronic alcoholism are associated with a marked decrease of plasma and parenchymal Mg2+, and Mg2+ administration is routinely used therapeutically. This study uses isolated rat hepatocytes to ascertain if and under which conditions increases in extracellular Mg2+ result in an increase in intracellular Mg2+. In the absence of stimulation, changing extracellular Mg2+ had no effect on total cellular Mg2+ content. By contrast, carbachol or vasopressin administration promoted an accumulation of Mg2+ that increased cellular Mg2+ content by 13.2 and 11.8%, respectively, and stimulated Mg2+ uptake was unaffected by the absence of extracellular Ca2+. Mg2+ efflux resulting from stimulation of α- or β-adrenergic receptors operated with a Mg2+:Ca2+ exchange ratio of 1. These data indicate that cellular Mg2+ uptake can occur rapidly and in large amounts, through a process distinct from Mg2+ release, but operating only upon specific hormonal stimulation.