Lack of effect of hypomagnesemia on elevated plasma 1,25-dihydroxycholecalciferol in acutely phosphate-deprived rats.

The effect of hypomagnesemia occurring in phosphate deprivation on elevated levels of plasma 1,25-dihydroxycholecalciferol (1,25(OH)2D3) was evaluated in rats. Phosphate deprivation was associated with an elevated plasma 1,25(OH)2D3, hypophosphatemia, and hypomagnesemia. With oral magnesium supplement during phosphate deprivation, plasma magnesium did not fall, but plasma inorganic phosphate fell and 1,25(OH)2D3 rose to comparable levels seen in phosphate-deprived rats lacking magnesium supplement. These results indicate that a rise in plasma 1,25(OH)2D3 during phosphate deprivation is not due to concomitant hypomagnesemia and support the postulate that phosphate deprivation per se is responsible for the elevated plasma 1,25(OH)2D3.