FREE CIRCULATING MAGNESIUM AND RENAL MAGNESIUM HANDLING DURING ACUTE METABOLIC-ACIDOSIS IN HUMANS

Ion-selective electrodes have been designed for determining the ionize d concentration of magnesium in blood, the biologically active form of this ion, The effect of acute acidosis induced by ammonium loading on circulating and urinary magnesium was investigated in 11 volunteers. No changes in plasma total and ionized magnesium were noted following administration of ammonium chloride. On the contrary, administration o f ammonium chloride increased the plasma free magnesium fraction and t he urinary magnesium excretion. The study demonstrates that the hyperm agnesuria induced by acute acidosis is not caused by ionized hypermagn esemia and supports the theory that acidosis decreases the circulating magnesium fraction that is bound to proteins.