Indomethacin inhibition of tenotomy-induced bone resorption in rats

Loss of biomechanical function results in rapid bone loss. This study assesses the role of arachidonic acid metabolites in immobilization-related osteopenia. A hind limb of the rat was immobilized by knee tenotomy and bone resorption and formation parameters were quantitated by histological methods in indomethacin-treated (0.5 mg/kg per day) and vehicle-treated animals. Control animals sacrificed 30, 72, and 240 hr post-tenotomy revealed a significant increase in osteoclast number (30 hr) and resorption surfaces (72 hr) and a decrease in trabecular bone volume (240 hr) in the tenotomized tibiae. In the indomethacin-treated tibial metaphysis, no significant differences were noted for these parameters by comparison to the nontenotomized leg. Bone formation parameters remained reduced in the tenotomized legs of both the indomethacin and vehicle-treated groups compared to the control legs. Indomethacin inhibited bone resorption, but did not prevent the decrease in bone formation produced by immobilization over the 10 days of these experiments.