1. Two studies were performed to determine the effects of acid stress and ovariectomy on bone metabolism in young rats. In Expt 1, eighteen female weanling Sprague-Dawley-descended rats were ovariectomized, placed in one of three dietary groups and given a diet containing (g/kg): 6 calcium and 3, 6 or 12 phosphorus for 10 weeks. In Expt 2, thirty-two female weanling Sprague-Dawley-descended rats were ovariectomized, and thirty-two were left intact. Eight rats from each group were given a diet containing (g/kg): 6 Ca and 3 P, 12 P, 3 P+1 S or 3 P+20 ammonium chloride for 10 weeks.
2. Feeding diets containing 12 g P/kg resulted in decreased serum Ca and increased urinary P with no changes in femur composition. Feeding high-sulphate and ammonium chloride diets resulted in increased urinary Ca and, when combined with ovariectomy, lower femur Ca and P with no changes in femur hydroxyproline or hexosamines.
3. The findings reflect the more rapid turnover of the amorphous calcium phosphate salts found in greater amounts in bones of younger animals than for more stable apatitic crystals that predominate in bones of older animals.