Stimulation of bone resorption by comparatively high dose of zinc in rats

The changes of femoral calcium and acid phosphatase activity were examined in rats orally administered zinc sulfate (10 mg Zn/100 g body weight) for 3 d. Zinc administration to intact rats produced significant decreases of calcium levels in the serum, and femoral diaphysis and epiphysis, while it caused remarkable remarkable elevation of acid phosphatase activity in the femoral diaphysis and epiphysis. Thyroparathyroidectomy significantly prevented the alterations of the calcium content and the enzyme activity in the femoral diaphysis and epiphysis caused by zinc administration to intact rats. The present results suggest that comparatively high dose of zinc may stimulate bone resorption mainly mediated through the actions of parathyroid hormone, due to maintain calcium homeostasis.