Osteoclast formation in response to intraperitoneal injection of 1 alpha-hydroxycholecalciferol in mice.

In order to assess osteoclast formation in response to 1 alpha-hydroxycholecalciferol, osteoclast counts per cm of bone surface were performed on paraffin sections of femurs of male CBA mice killed at daily intervals up to 5 days. All animals received daily intraperitoneal injections of 1 alpha-hydroxycholecalciferol up to the time of death. Peak osteoclast formation occurred during the third day, by the end of which maximum numbers of osteoclasts were achieved (11.9 +/- 0.9 osteoclast cm-1) compared to controls (3.5 +/- 0.6 osteoclast cm-1), this increase being highly significant (p less than 0.01). Although the osteoclast population was most dense at the metaphyseal plate in both experimental and control groups, osteoclast counts in this region only doubled whereas overall osteoclast counts more than tripled. The number of nuclei per osteoclast did not significantly alter following four daily injections of 1 alpha-hydroxycholecalciferol.