Effect of Dietary Magnesium on the Development of Nephrocalcinosis in Rats

Abstract

Weanling rats fed a semipurified diet containing 0.4% Ca, 0.56% P and 0.05% Mg rapidly developed a nephrocalcinosis in which deposits of calciumphosphate mineral formed in the region of the corticomedullary junction of the kidney. Calcification was more severe in female rats than in male rats. Because 0.05% Mg is considered an adequate dietary level, and because both serum and kidney content of magnesium were normal, the calcification in the kidneys was not likely to have developed as a result of a simple dietary magnesium deficiency. However, raising the dietary magnesium to 0.45% with either magnesium chloride or magnesium carbonate increased serum magnesium and prevented the development of nephrocalcinosis. The protective action of magnesium could not be explained by alterations in the concentrations of calcium and phosphorus in the serum. When the supplemental magnesium was provided as carbonate, renal and bladder calculi composed principally of magnesium and phosphorus formed quickly, probably because of a high concentration of magnesium in an alkaline urine.