Effects of running exercise on tibiae in ovariectomized rats

Abstract

The effects of running exercise on bone histomorphometric parameters were examined in sham-treated (Sham) and ovariectomized (OVX) rats. The rats were either kept sedentary (C) or trained (T) on a rodent treadmill at 25m/min, 30 min/day, 5 days/week for 10 weeks. Fat-free dry bone weight, bone mineral content (BMC), and histomorphometric parameters were assessed after excision of the tibiae at sacrifice. The results are summarized as follows : 1) There were no significant differences in fat-free dry bone weight and BMC between OVX-C and Sham-C rats. However, BMC/body weight in OVX-C rats was significantly lower than in Sham-C animals. OVX-C rats had significantly lower trabecular bone volume at the proximal tibial metaphysis than Sham-C animals. Values of bone formation parameters were significantly higher in OVX-C rats than in Sham-C animals. 2) BMC/body weight in OVX-T rats was significantly higher than in OVX-C animals. OVX-T rats had a significantly higher trabecular bone volume at the proximal tibial metaphysis than OVX-C animals. There were no significant differences in bone formation parameters between OVX-T and OVX-C rats. 3) No significant differences were found in any parameters between sham-C and Sham-T rats. These results suggest that (1) running exercise has a suppressive effect on bone loss after OVX, and (2) training-induced reduction of bone loss by OVX does not seam to be associated with facilitation of bone formation but with suppression of bone resorption.