TISSUE DISTRIBUTION AND TRANSPORT OF ELECTROLYTES MG28 AND CA47 IN HYPERMAGNESEMIA

The effect of acute hypermagnesemia (9-14 meq/1) on the distribution of electrolytes Mg28 and Ca47 in various tissues was studied in renal-ligated dogs. The sodium content of 5 of 8 tissues was decreased by 10-30 percent, the K content of 3 tissues was increased 5-30 percent and the acid-soluble P concentration of 2 tissues was decreased by 15 percent. Total and/ or exchangeable cellular concentrations of Ca were decreased by 25-35 percent in skeletal muscle, myocardium, brain and pancreas. Total and/or exchangeable cellular concentrations of magnesium were increased by 8-50 percent in skeletal muscle, nerve, pancreas and aorta and were unchanged in liver, myocardium and brain. These data suggest that Mg has inhibitory effects on the cellular transport of electrolytes which are similar to those of Ca. The cellular influx of Ca is inhibited by Mg. The stability of the cellular concentrations of Mg in relation to the degree of hypermagnesemia is compatible with in vitro studies in rat liver indicating that the fractional rate of cellular influx of Mg is decreased and the fractional rate of cellular efflux of Mg is increased during extreme hypermagnesemia.