A direct effect of 24,25-(OH)2D3 and 1,25-(OH)2D3 on the modeling of fetal mice long bones in vitro

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Abstract
To examine the effects of 24,25‐(OH)2D3 and 1,25‐(OH)2D3 on fetal long bone modeling the radii and ulnae of 16 day fetal mice were grown in vitro for 2 days. Their growth, mineralization, and resorption were assessed by measuring diaphyseal length, calcium and phosphorus content, hydroxyproline‐protein ratios, and the release of incorporated 45Ca. The results showed that 24,25‐(OH)2D3 at concentrations of 10−10‐10−8 M stimulated the growth of the bones as indicated by their increased diaphyseal length, periosteal bone area, and hydroxyproline content. Calcium and phosphorus content was significantly increased; 45Ca release was unaltered. Bones incubated in media containing 10−6 M 24,25‐(OH)2D3 responded in a similar fashion to bones incubated in media containing 10−10‐10−8 M 1,25‐(OH)2D3, with inhibition of bone growth as indicated by reduced diaphyseal length, periosteal bone area, hydroxyproline‐protein ratios, and calcium and phosphorus content; 45Ca release was significantly increased. Neither metabolite affected total bone length. The results suggest a role for 24,25‐(OH)2D3 in the growth of fetal mice bones in vitro and also confirm the findings from previous studies that 1,25‐(OH)2D3 and high concentrations of 24,25‐(OH)2D3 stimulate bone resorption.
Funding Information
  • USA-Israel Binational Fund (2246)
  • Teva Pharmaceuticals (032-4128)