Phosphaturia in magnesium-deficient rats

Abstract

The effect of magnesium defiency on urinary phosphate excretion was studied in rats rendered magnesium deficient by diet. Increased urinary phosphate excretion was observed. Tubular maximum reabsorption (Tm) of inorganic phosphate was lower in magnesium-deficient (0.9 [plus or minus] 0.2 [mu]M/ml per min.) than control animals (1.9 [plus or minus] 0.3 [mu]M/ml per min, P< .001). Since hypomagnesemia was accompanied by hypercalcemia, Tm of in-organic phosphate was measured in parathyroidectomized rat. In this group the low-magnesium animals had a Tm of 1.9 [plus or minus] 08 [mu]M/ml per min. compared to 4.3 [plus or minus] 0.5 [mu]M/ml per min. in controls, PP< .001. It is concluded that the phosphoruresis of hypomagnesemia is not due solely to hyperparathyroidism. The reponsible mechanism remains elusive.