Comparison of therapeutic usefulness of vitamin D3 analogs on osteoporosis caused by ovariectomy in rats.

Ovariectomy induced a remarkable reduction in the ash content of the femur and histologically a disappearance of the trabecular bone in tibial metaphysis accompanying the decrease of serum calcium level and urinary calcium excretion in young immature rats. Treatment with 1 alpha-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and 1,24R-dihydroxyvitamin D3 for 3 months from 7 to 9 months after the ovariectomy dose-dependently increased serum and urinary calcium, bone ash, and histologically partly improved a loss of trabeculae. The 24R,25-dihydroxyvitamin D3 doses, on the other hand, produced no therapeutic effect on the bone disorders in ovariectomized rats, except for the slight effect on the increasing activity of serum calcium.