1,25-Dihydroxyvitamin D3 prevents the decrease of bone mineral appositional rate in rats with inflammation-mediated osteopenia (IMO).

We have studied the effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on bone mass and bone mineral appositional rate in intact rats and rats with inflammation-mediated osteopenia (IMO), where osteoblast number and mineral appositional rate are decreased. 1,25(OH)2D3 prevents IMO-specific bone loss when given in a daily dose of 25 ng per rat, but does not when given in higher doses. The hormone was effective, when given over the complete duration of the experiment (21 days), but not when given over shorter time periods (7 and 14 days, respectively). 1,25(OH)2D3 prevents IMO-dependent reduction in mineral appositional rate and leads to an only moderate increase in intact rats. We conclude, that 1,25(OH)2D3 is more effective in stimulating mineral appositional rate in rats with IMO where mineral apposition is impaired.