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 (l, 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 l, 25(OH)₂D₃ rose to comparable levels seen in phosphate-deprived rats lacking magnesium supplement. These results indicate that a rise in plasma l, 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.