26,27-Hexafluoro-1,25-dihydroxyvitamin D3 (F6-1,25(OH)2D3) prevents osteoporosis induced by immobilization combined with ovariectomy in the rat.

The effect of 26,27-hexafluoro-1,25-dihydroxyvitamin D3 (F6-1,25(OH)2D3) on experimental osteoporosis in the rat induced by a combination of immobilization and ovariectomy was evaluated. F6-1,25(OH)2D3 increased the femur score and the photo-density. The administration of F6-1,25(OH)2D3 also significantly increased the dry weight, the ash weight and the ash content of the bone. Both F6-1,25(OH)2D3 and 1 alpha(OH)D3 showed a nearly dose-dependent effect and significant inhibition of the decrease of bone mass. Histomorphometry revealed a significant decrease of resorption by the administration of F6-1,25(OH)2D3. Bone formation rate in the F6-1,25(OH)2D3 treated group significantly decreased compared with the vehicle group. In conclusion, the pharmacological effective dose of F6-1,25(OH)2D3 was considered to prevent the osteoporotic decrease of bone mass by suppressing the elevated bone turnover.