Differential effects of calcium-regulating hormones on bone metabolism in weanling rats orally administered zinc sulfate

Abstract The effect of calcium-regulating hormones on bone metabolism was investigated in weanling rats orally administered zinc sulfate. Administration of 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ( 150 ng 100 g BW ) or parathyroid hormone (1–34) (PTH) ( 10 U 100 g ) produced significant increases in alkaline phosphatase activity and DNA content in the femoral diaphysis, while calcitonin (CT) ( 1.0 U 100 g ) did not have a significant effect. Administration of zinc ( 1.0 mg 100 g ) caused a significant elevation of alkaline phosphatase activity and DNA content in the femoral diaphysis. In combination with these hormones and zinc, both 1,25(OH) 2 D 3 and zinc caused a synergistic increase in diaphyseal alkaline phosphatase activity and DNA content, while the combination with zinc and PTH, or zinc and CT did not cause a synergistic increase. The synergistic effects in combination with 1,25(OH) 2 D 3 and zinc were completely inhibited by treatment of mitomycin C ( 10 μg 100 g ). Meanwhile, the increase in diaphyseal zinc content following zinc administration was not altered by treatment with 1,25(OH) 2 D 3 . These results indicate that zinc synergistically enhances 1,25(OH) 2 D 3 -stimulated bone metabolism. This suggests a physiologic significance of zinc in the regulation of bone metabolism.