Vitamin D and Citrate Metabolism

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Abstract
Three-week-old rats fed a vitamin D-deficient diet adequate in calcium and phosphorus show biochemical evidences of vitamin D deficiency without the characteristic bone changes of rickets. The significant findings are hypocalcemia and reduction of the concentrations of citrate in serum and bone with normal serum phosphorus levels. Body weight gain and bone weight increments are reduced in the vitamin D-deficient rat. One hundred units of vitamin D increases the serum calcium and citrate levels and the concencentration of bone citrate. Vitamin D-deficient rats show no response to parathyroid extract unless primed with vitamin D before injection of parathyroid extract. Feeding of cortisol to the vitamin D-deficient rat reduces serum and bone citrate concentrations and blocks the enhancing effect of vitamin D upon citrate levels. There is no necessary correlation between the concentration of citrate and of calcium in serum and suppression by cortisol of the vitamin D effect upon citrate concentrations does not inhibit the vitamin D effect upon calcium levels in serum.