MINOCYCLINE PREVENTS THE DECREASE IN BONE-MINERAL DENSITY AND TRABECULAR BONE IN OVARIECTOMIZED AGED RATS

In the current study, we examined the effects of minocycline, on the o steopenia of ovariectomized aged rats, Old female rats were randomly d ivided into five groups: sham, ovariectomized control and ovariectomiz ed treated with minocycline, 17 beta-estradiol, or both agents, Bone s amples were collected 8 wk after the treatment, Ovariectomy reduced bo ne mineral density of the whole femur and at the condylar, distal meta physeal and head-neck-trochanter regions 10%-19% and the loss of bone density was prevented by treatment with minocycline or 17 beta-estradi ol. Histomorphometric analysis of distal femur showed ovariectomy redu ced the trabecular bone area, the trabecular bone number, trabecular b one thickness and increased the trabecular bone separation, The microa natomic structure of trabecular bone also showed that the number of no des, node to node, cortical to node, node to free end was reduced by o variectomy, Treatment with minocycline attenuated the effect of ovarie ctomy on trabecular bone in aged animals, In contrast, cortical bone w as not affected by ovariectomy or minocycline treatment, The effect of minocycline on bone turnover was also examined, Minocycline increased osteoid surface, mineralizing surface, mineral apposition rate, bone formation rate and reduced eroded surface. We have therefore concluded that the modest increase in bone mineral density and the improvement in the trabecular bone status noted in minocycline treated ovariectomi zed aged rats is likely due to an increase in bone formation coupled w ith a decrease in bone resorption. (C) 1996 by Elsevier Science Inc.