[Feedback of the magnesium ion on the parathyroid hormone: differences in the action of magnesium sulfate and pyrrolidone carboxylate].

Fourty-five minutes after an intravenous injection of Mg SO4 (170 mg of element Mg), in 7 young and healthy men, a significant decrease in circulating 53-84 PTH has been observed. An injection of magnesium pyrrolidone carboxylate (170 mg of Mg) failed to induce changes in plasma levels of PTH. The urinary excretion of Mg was 2-fold higher after the injection of Mg SO4 than after the injection of magnesium pyrrolidone carboxylate. For both magnesium salts used, the time patterns of plasma magnesium concentrations were the same and red blood cells magnesium was not increased. These results suggest that, in our experimental conditions, the retention of magnesium was higher after magnesium pyrrolidone carboxylate than after Mg SO4 and that the drop in plasma PTH could partly explain the larger urinary excretion of magnesium after Mg SO4.