Biochemical markers of bone resorption in ovariectomized rats: therapeuticeffects of vitamin D metabolites

The changes of bone metabolism in female rats after ovariectomy are similar to the alterations in early post-menopausal women. Vitamin D metabolites, especially the naturally occurring steroid hormone 1,25-dihydroxyvitamin D- 3, are known to prevent bone resorption, but show negative side-effects suc h as hypercalcaemia and hypercalciuria. This study focused on 1 alpha-hydro xyvitamin D-3, on 1 alpha-hydroxyvitamin D-2 and on 1,25-dihydroxyvitamin D -2. The application of 1,25-dihydroxyvitamin D-3, 1 alpha-hydroxyvitamin D- 3 and 1,25-dihydroxyvitamin D-3 proved to be effective in decreasing bone r esorption in ovariectomized rats. However, these vitamin D metabolites indu ced the negative side effects of hypercalcemia and hypercalciuria. The appl ication of 1 alpha-hydroxyvitamin D-2 led to an adjustment of markers of bo ne resorption altered by ovariectomy to the corresponding values of control animals without increasing the values for serum and urinary calcium. This vitamin D metabolite could represent an interesting alternative to 1,25-dih ydroxyvitamin D-3, which is the dominating substance in the prophylaxis of postmenopausal osteoporosis with vitamin D metabolites.