EFFECT OF TREADMILL EXERCISE AND OVARIECTOMY ON FEMORAL AND LUMBAR VERTEBRAE IN YOUNG AND ADULT-RATS

The aim of this study was to examine the effect of exercise training on long bone and vertebra in young and adult ovariectomized rats. Female Sprague-Dawley rats, aged 6 weeks (young) and 10 months (adult) were divided into four groups: sham-operated control, ovariectomized, sham-operated exercised and ovariectomized exercised. The animals were pre-labeled with H-3-tetracycline for evaluation of bone resorption. Ovariectomy resulted in increased bone resorption in both the femur and fifth lumbar vertebra (L-5) of young and adult rats as determined by H-3-tetracycline retention in bone. The calcium content of L-5, but not of the femur, was also decreased by ovariectomy in these rats. Exercise increased the calcium content in both the femur and L-5 of the sham-operated and ovariectomized young rats. These results are consistent with increased bone retention of H-3-tetracycline by exercise, suggesting that exercise suppresses bone resorption. In adult rats, the effects of exercise on bone were not as consistent as those in young rats. In sham-operated animals, exercise significantly increased femoral calcium content. With ovariectomy, however, vertebral calcium content was significantly suppressed by exercise. In conclusion, exercise in young rats decreases both basal and ovariectomized-induced bone resorption and increases femoral and vertebral bone mass in ovariectomized animals. In adult rats, these effects were not apparent under the conditions of treadmill training used in this experiment.