ABSTRACT
There is increasing evidence suggesting the role of free radicals in bone resorption and bone loss. Ovariectomized rats have been used as animal models for the study of osteoporosis. Oxidative stress due to reactive oxygen species [ROS] can cause oxidative damage to cells. Even though, there are studies suggesting the role of free radicals in bone loss, however, the preventive role of exercise on oxidative stress remains obscure. The aim of the present study was to investigate the impact of ovariectomy [OVX] on bone and the possible effects of swim-training regimen on the bone turnover markers and oxidant/antioxidant system in adult rats. The present study was carried out on thirty female albino rats classified into 2 groups. Group I [n=10] underwent sham operation, while group II [n=20] underwent bilateral Ovariectomy [OVX]. Eight weeks after OVX, 10 rats of group 2 [group II a] were left for free cage movement while the other 10 rats [group II b] started to practice swim-training regimen for 1 hour daily, 5 days per week, for 7 weeks. Fifteen weeks from the start of the experiment, blood and urine samples were taken for estimation of biochemical markers of bone turnover [calcium, phosphorous, alkaline phosphatase [ALP], Osteocalcin [OC] and urinary deoxypyridinoline [DPD]]. Then, the rats were killed and the femora were removed. The bone tissue homogenates were used for the estimation of oxidant/antioxidant system markers [superoxide dismutase [SOD], glutathione peroxidase [GPx], malondialdehyde [MDA] and hydrogen peroxide [H2O2]]. The results showed that OVX induced bone oxidative stress with in- creased levels of MDA and H2O2 associated with decreased activity of SOD and GPx significantly when compared to control sham-operated rats. Serum ALP, OC and urinary DPD were elevated significantly in the sedentary OVX rats compared to the sham-operated control rats. Swimming exercise improved OVX-induced bone oxidative stress with significantly lower levels of MDA and H2O2 associated with higher levels of SOD and GPx in exercised rats when compared to sedentary OVX rats. Similarly, exercise limited OVX-induced increase in bone turnover by suppression of serum ALP, OC, and urinary DPD levels. It was concluded that OVX in rats induced bone oxidative stress with increased bone turnover and altered its biochemical markers. Short-term swimming exercise for 7 weeks partially stabilized bone turnover and improved oxidative stress but not able to fully reverse the abnormalities induced by OVX. Further researches are indicated to detect the effect of long-term exercise especially on bone mineral content and density