Abstract
A study was undertaken to evaluate the effects of 1, 24(R)-dihydroxyvitamin D3(1, 24(R) (OH)2D3) and 1, 25-dihydroxyvitamin D3(1, 25(OH)2D3) on the metabolic bone disorder developed in forced swimming rats. Serum 1, 25(OH)2D concentration was significantly lower in the swimming group than in the intact group. Neither serum levels of calcium, phosphorus and immunoreactive parathyroid hormone(iPTH) nor urinary excretions of calcium and phosphorus are significantly different between the intact and the swimming groups. The ash content of the tibia significantly decreased in the swimming rats, and histological changes in longitudinal sections of the tibia from the swimming rats were quite similar to the osteoporosis. The oral administration of 1, 24(R)(OH)2D3 and 1, 25(OH)2D3(0.10μg/kg/day, from the 49th to the 81st days of forced swimming) increased the ash content of the tibia and partially prevented development of osteoporosis in the swimming rats. These results might indicate that these vitamin D3 therapy is effective for the osteoporosis caused by the severe exercise.
