Are there differences between Sprague-Dawley and Wistar rats in long-term effects of ovariectomy as a model for postmenopausal osteoporosis?

Ovariectomized Sprague-Dawley (SD) and Wistar rats are widely used as animal models for postmenopausal osteoporosis. This study aimed to investigate differences in the long-term effects of ovariectomy on these two breeds of rats. 6-month-old SD and Wistar rats underwent sham operation (Ssham and Wsham) or bilateral ovariectomy (Sovx and Wovx). Body weight, absolute fat, fifth and sixth lumber vertebrae (L5-6) bone mineral density (BMD), and whole body bone mineral content (BMC) were evaluated from 14 to 68 weeks after operation. Body weight significantly increased compared to shams at every point (except 68 weeks) for Sovx and at 14, 21 and 38 weeks for Wovx (all P < 0.05), the increases were not significantly different between breeds. Absolute fat increased significantly compared to shams at every point (except 14 and 68 weeks) for Sovx and at 30 weeks for Wovx (all P < 0.05), the increases were significantly different between Sovx and Wovx (P = 0.007), but not the shams. L5-6 BMD increased then decreased and was significantly lower than shams at 30, 38 and 50 weeks for Sovx and at 14 weeks for Wovx (all P < 0.05), the initial increases were significantly different between Sovx and Wovx (P = 0.006), but not the shams. BMC was significantly decreased compared to sham groups at every point (except 14 and 68 weeks) for Sovx and at 14, 21, 38, and 50 weeks for Wovx (all P < 0.05), the decreases were not significantly different between breeds. In conclusion, ovariectomy had a greater effect upon absolute fat and L5-6 BMD in SD rats.