Enhancement of vitamin D3 effect on bone metabolism in weanling rats orally administered zinc sulphate.

The interaction of vitamin D3 and zinc on bone metabolism was investigated in the femur of weanling rats. Oral administration of vitamin D3 (1.0 micrograms/100 g body weight) did not cause any increase in the zinc accumulation in the femoral tissue following treatment with zinc sulphate (1.0 mg Zn/100 g). Administration of vitamin D3 or zinc produced significant increases the alkaline phosphatase activity and DNA content of the femoral diaphysis but not of the epiphysis. The increase in alkaline phosphatase activity was enhanced additionally by simultaneous administration of vitamin D3 and zinc. Moreover, the increase in DNA content was enhanced markedly (about 4 times) by these treatments. At a dose of 0.5 micrograms of vitamin D3 per 100 g, DNA content was at the control level. This level was increased about 2 times by simultaneous administration of zinc (1.0 mg/100 g). The increase in alkaline phosphatase activity following simultaneous administration of vitamin D3 and zinc was significantly inhibited by treatment with cycloheximide, actinomycin D, or mitomycin C. Also, the increase in DNA content was completely inhibited by mitomycin C treatment. The present data suggest that the combination of vitamin D3 and zinc has a multiple effect on the stimulation of bone growth and mineralization in weanling rats, and that this effect is based on a stimulation of the DNA synthesis in bone cells.