Effects of vitamin D3 metabolites in ovariectomized rats.

The effects of two vitamin D3 metabolites, 24R,25-dihydroxyvitamin D3 and 1 alpha,25-dihydroxyvitamin D3, were investigated in ovariectomized rats. The amount of ash in the femur on a defatted dry weight basis was significantly greater in rats treated with 1 microgram/kg 24R,25-dihydroxyvitamin D3, or 0.01 or 0.1 microgram/kg 1 alpha,25-dihydroxyvitamin D3 than in the controls. The concentration of bone gla protein in serum and amounts in the femur were significantly greater in rats treated with 1 or 10 micrograms/kg 24R,25-dihydroxyvitamin D3, but not those given 1 alpha,25-dihydroxyvitamin D3 compared with the controls. These results suggest that 24R,25-dihydroxyvitamin D3 increased bone mass probably through the stimulation of bone formation.