EFFECTS OF PHYSICAL EXERCISE ON FEMORAL BONE MINERAL DENSITY AND OSTEOCYTE MICROMORPHOLOGY IN YOUNG OVARIECTOMIZED (OVX) RATS

To investigate the effects of exercise on femoral regional bone mineral density and osteocyte micromorphology in young ovariectomized (OVX) rats, animals were divided into an ovariectomized group (OVX group), an ovariectomized + exercise group (OVX + exercise group), and a sham surgery group (SHAM group). Femoral bone mineral density was significantly lower in the OVX and OVX + exercise groups than in the SHAM group. A large difference in bone mineral density in the distal femoral epiphysis was observed between the OVX and OVX + exercise groups. In the OVX group, bone lacunae showed less immunostaining for DMP-1 (dentin matrix protein-1) and osteocyte processes were fewer than in the SHAM group. In the OVX + exercise group, osteocyte processes were thicker (0.44 to 0.66 mu m) than in the OVX group (0.22 to 0.26 mu m). These results indicate that exercise induced structural changes in the femur, including formation of osteocyte processes and strengthening of the communication network between osteocytes. (Jpn. J. Phys. Fitness Sports Med. 2010,59 : 395-406)