Effects of dietary supplementation of calcium and vitamin don bone growth in growing male rats

Abstract

Effects of dietary supplementation of calcium (Ca) and vitamin D(D) on bone growth in growing male rats were investigated. We performed this study using D-deficient rats of 3-month-old. In the experiment 1, the D-deficient rats were fed either low-Ca (0.22% Ca) or high-Ca (1.20% Ca) diets with oral supplementation of different amounts of D₃ (0, 0.7, 7 or 70 IU/week) for 28 days. In the dxperiment 2, the D-deficient rats were fed diets containing different concentrations of Ca (0.22, 0.44, 0.88 or 1.20%) with oral D₃ supplementation of either low-dose (0.7 IU/week) or relatively high-dose (70 IU/week) for 28 days. After the feeding period, plasma levels of Ca, 1α, 25 (OH)₂D₃, PTH, bone Gla protein were measured. Bone ash weight, bone mineral density, mechanical bone strength were also measured. In the both experiments, the plasma levels of PTH decreased to the normal levels in response to the increased amounts of dietary Ca intakes as well as D supplementation. In contrast, the bone markers increased to the respective normal levels in response to the increased amounts of dietary Ca intakes as well as D supplementation. In the experiments 1 and 2, a high correlation between the plasma levels of PTH and the bone markers was observed. These results suggest that both dietary Ca and D supplementation may affect bone growth in growing rats by controlling PTH secretion.