Niacin Ameliorates Hypercalciuria and Hyperphosphaturia Due to Glucocorticoid Administration in Rats

Hypercalciuria and hyperphosphaturia are present in long term and high dose regimens of glucocorticoid therapy. This study aims to evaluate the effect of niacin at its pharmacological dose on calcium and phosphate disturbances due to methylprednisolone administration in growing rats. Twenty one rats were randomly divided into three equal groups and treated as follows for 4 weeks: 1-Normal saline (Control); 2-Methyl Prednisolone (MP) acetate, 3.5 mg kg^-1 five days a week, SC and 3- MP acetate, 3.5 mg kg^-1 five days a week, SC + niacin 200 mg kg^-1 daily by oral gavages. At the end of the experiment, serum and urinary calcium and phosphate assays were performed and calcium content of forth lumbar vertebrate and tibia-fibula bone was determined by atomic absorption method. No significant difference observed in serum calcium or phosphate levels among different groups (p>0.05), however an obvious hypercalciuria associated with hyperphosphaturia was present in MP group as compared to control (p<0.001). Niacin significantly decreased urinary calcium (p<0.001) and phosphate (p = 0.005) concentrations as compared to MP group. Calcium level was still significantly higher than control (p<0.001), while phosphate decreased even to a lower level than control (p = 0.005). Calcium content of forth lumbar vertebrate or tibia-fibula bone of rats remained statistically the same among different groups (p>0.05). Niacin at its pharmacological dose can ameliorate hypercalciuria and hyperphosphaturia due to long term and high dose glucocorticoid administration in growing rats without affecting bone calcium content. The possible clinical importance of this effect needs to be clarified in future studies.