Ovariectomy, dietary zinc, and bone metabolism in retired breeder rats

Bone mineral turnover was studied in sham and ovariectomized (ovax) retired breeder rats after 16 wk of dietary treatment. Rats were fed either a commercial rat diet (CRD) containing high calcium and cholecalciferol or egg-white diets (EWD) containing 2 g Ca/kg, 1,25-(OH)2cholecalciferol (5 micrograms/kg), and either 10 or 200 mg zinc/kg. In rats fed EWD, high Zn enhanced femoral Zn deposition and concentration but did not affect serum Ca levels, bone mineral content (BMC), or turnover. Serum Ca levels and BMC were greater in sham rats and there was a gain in femoral Ca and phosphorus compared with the loss of these minerals in ovax rats. In CRD-fed ovax rats, values for these variables were similar to those of CRD-fed shams and there was no bone mineral loss. These data suggest that ovarian function may be a prerequisite for the beneficial effects of diets containing 1,25-(OH)2cholecalciferol and low Ca on bone metabolism.