MAGNESIUM-DEPENDENT CALCIUM EFFLUX IN MAMMALIAN HEART-MUSCLE

Extra and intracellular magnesium is involved in the control of myocar dial calcium movements. Here we report on an increase in cytosolic cal cium concentration in resting Ventricular myocytes due to the withdraw al of extracellular magnesium under the condition of a blocked sodium- dependent calcium elimination. Evidence for an activation of cellular calcium efflux by extracellular magnesium showed experiments in perfus ed hearts. It is concluded that extracellular magnesium can modulate t he intracellular free calcium concentration of the myocardial cell by its influence on calcium elimination.