The action of magnesium in reducing renal calcification in rats receiving high phosphorus supplemented diet

Abstract

The changes in the concentrations of calcium in kidney and secreted hormone were studied in weanling male rats fed diets either high in phosphorus as phosphate or high in both phosphorus and magnesium. In the first experiment, the rats were fed formulated diets containing 0.05% magnesium added as magnesium sulfate and either 0.5% or 1.5% total phosphorus added as K 5P 3O 10. Calcium and phosphorus concentrations in the kidneys of rats fed the high phosphorus diet were significantly elevated. In addition urinary excretion of calcium was decreased and that of phosphorus was increased by high phosphorus administration. The high phosphorus diet also produced significant increase in serum PTH without increase in urinary cAMP excretion. In the second experiment, the rats fed the same formulated diets supplemented with either 0.05% or 0.20% magnesium added as magnesium sulfate after 3 weeks of 1.5% total phosphorus added as K 5P 3O 10 supplementation. Increasing the intake of magnesium decreased calcium concentration in kidney although serum PTH was still elevated. In conclusion, the effect of magnesium to protect against phosphorus-induced nephrocalcinosis was related with renal receptivity for PTH action.