Morphometric evidence that YM175, a bisphosphonate, reduces trabecular bone resorption in ovariectomized dogs with dietary calcium restriction.

We examined mechanisms by which incadronate disodium (YM175) prevented bone resorption in ovariectomized dogs with dietary calcium restriction using the morphometrical method. YM175 (0.01-1.0 mg/kg) was given to ovariectomized dogs for 18 months. Because lumbar bone mineral density remained constant at month 17, we assumed that the trabecular bone resorption rate was equal to the bone formation rate and that wall thickness equaled resorption cavity depth. YM175 decreased both the bone resorption rate per number of osteoclasts and resorption cavity depth of cancellous pockets which were increased in ovariectomized dogs. These results suggest that YM175 reduces bone loss by decreasing the resorbing activity of osteoclasts.