The effect of ovariectomy on bone metabolism in rats.

It is well known that the ovariectomized rat is a good model for osteoporosis. Recently, it has been possible to measure the bone mineral density (BMD) of small animals accurately using dual energy X-ray absorptiometry (DXA). Therefore, in this study the change in the BMD in the different bone structures was examined in in vivo using aged and growing rats. The BMD of the lumbar spine and the tibial proximal metaphysis, which are mainly trabecular bone, in ovariectomized aged and growing rats with ovariectomized was significantly lower than those of the control (sham) group. However, the BMD of the tibial diaphysis, which is mainly cortical bone, showed no change nor had a tendency to decrease in the early stages of the experiment. These results suggest that it is important to take into account the age and the bone site in order to evaluate the experiment, which uses the rat model with ovariectomized osteoporosis.