Does endurance running before orchidectomy prevent osteopenia in rats?

This experiment was performed to study the effects on femoral bone of endur ance training performed during the 3 months before orchidectomy in rats whi ch were then killed 90 days later. A total of 70 male Wistar rats were used at 8 weeks old. One day 0 of the experiment, 10 rats were killed by cervic al dislocation and used as first controls. Among the 60 others, 30 were sel ected for treadmill running (60% maximal oxygen uptake, 1 h . day(-1), 6 da ys . week(-1) for 90 days). The 30 other rats remained at rest. On day 90, 10 exercised (IE) and resting (IR) rats were killed and used as intermediar y controls. Among the 20 other animals of each group, 10 were surgically ca strated (CXE, CXR) or 10 sham-operated (SHE, SHR) and killed on day 180. On day 90 femoral failure load (three-point bending test) was greater in IE t han in IR. Simultaneously, the deoxypyridinolinuria was lower in IE than in IR. On day 180, femoral bones were thinner in CXR than in CXE. The lowest values for trabecular bone are in the distal femoral metaphysis were measur ed in CXE and CXR rats, but the value measured in CXE was no different from that measured in SHR. Simultaneously total femoral bone density was lower in CXR than in SHE, while no difference concerning femoral metaphyseal dens ity was observed between CXE and SHR. These results confirmed that enduranc e running increased femoral bone growth and modelling and femoral trabecula r area, and thereby peak bone mass, in 8-month-old male rats. In resting an imals, castrated after the training period, androgen deficiency decreased f emoral density, mineral content and trabecular area. This decrease was not observed in castrated but previously exercised rats. Thus, by increasing pe ak bone mass, it was considered that endurance training may have a preventi ve effect against orchidectomy-induced bone loss.