Phosphaturia in magnesium-deficient rats.

GINN, H. EARL, AND LINDA L. SHANBOUR. Phosphaturia in magnesium-dejcient rats. Am. J. Physiol. 2 12(6) : 1347-1350. rg67.-The effect of magnesium deficiency 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 =t 0.2 &ml per min) than control animals ( I .g =t 0.3 PM/ml per min, P < .OOI). Since hypomagnesemia was accompanied by hypercalcemia, Tm of inorganic phosphate was measured in parathyroidectomized rats. In this group the low-magnesium animals had a Tm of I .g =t 0.8 &ml per min compared to 4.3 9~ 0.5 &ml per min in controls, P < .ooI. It is concluded that the phosphoruresis of hypomagnesemia is not due solely to hyperparathyroidism. The responsible mechanism remains elusive.