The effect of prednisolone on kidney calcification in vitamin D-treated rats.

Glucocorticoids are often used to treat hypercalcemia due to vitamin D overdosage. We measured the effect of 1.5 mg/day of prednisolone on the amount of calcium deposited in the kidney of rats dosed with either 500 ng/d or 2000 ng/day of 1-alpha OHD2 or 1-alpha OHD3. The rats were given a diet containing 0.3% calcium and 0.5% phosphate. A second group of rats received 2000 ng/d of the vitamin D analogs and a diet which contained only 0.02% calcium. After 6 weeks, rats given the vitamin D analogs had two to six times more calcium in the kidney compared with the controls (0.096-0.276 mg vs. 0.240-1.064 mg). When a pharmacological dose of prednisolone was added to treatment, calcium in renal tissue increased to 0.305-3.083 mg. The urinary output of calcium seemed to be increased by prednisolone whereas the serum calcium was lowered. It appears that glucocorticoids given at the same time as vitamin D compounds increases the risk for nephrocalcinosis possibly due to increased amounts of calcium in the urine.