CALCIUM-METABOLISM AND BONE MINERALIZATION IN FEMALE RATS FED DIETS MARGINALLY SUFFICIENT IN CALCIUM - EFFECTS OF INCREASED DIETARY CALCIUM INTAKE

Experiments were carried out to determine the ability of female rats with poorly mineralized skeletons to increase bone mineralization in response to increased dietary Ca consumption. We specifically addressed this question with regard to two different periods of the life cycle: the period of sexual maturation (6-9 weeks of age), and in animals that had attained adult rates of skeletal mineralization (100 days of age). We found that at both stages, increased dietary Ca consumption resulted in increased trabecular bone volume and total bone Ca. In the younger animals, it was found that dietary history influenced the disposition of bone mineral. Animals that were initially Ca-deprived exhibited increased trabecular bone and decreased cortical thickness compared to animals continuously fed 0.5% Ca. Ovariectomy of mature animals reduced but did not eliminate the response to increased Ca intake.