[Magnesium metabolism in chronic lead poisoning: influence of chelating treatment]

Thirteen patients with chronic lead poisoning were compared to 13 healthy subjects for magnesium in blood (plasma and erythrocytes) and in 24-hour urine, and serum and urinary Ca and P. Determinations were made before an infusion of 1 g Ca EDTA and on the following day. In the basic state, all the parameters were identical in both groups. Ca EDTA elicits a significant drop in plasma Mg only in the patients with lead poisoning, without modifications of erythrocytic or urinary Mg. Consequently, the drop in plasma Mg might be due to a shift from an extracellular to a tissue pool. This shift might be cause by the action of EDTA itself, or might be the consequence of removal of lead from cellular sites of fixation, where it could be replaced by Mg ions.