Rat Model of Postmenopausal Osteoporosis

Many studies had shown that 6-month-old female rat ovariectomized bilaterally was a good model for postmenopausal osteoporosis [32 (link),33 (link)]. We obtained a total of 72 6-month-old virgin Wistar rats with body weight of 310 ± 20.0 g from the Experimental Animal Center of Academy of Military Medical Sciences (SCXK-(Military) 2002-001, Beijing, China). The Institutional Ethics Committee of China Academy of Chinese Medical Sciences approved the experimental research on the animals. The acclimatized rats were either Sham-operated (SHAM, n = 12) or bilaterally ovariectomized (OVX, n = 60) using the dorsal approach [41 (link)]. The OVX rats were randomly divided into five groups: OVX group (OVX, n = 12); estradiol valerate treatment group (OVX + EV, n = 12); DG high-dose treatment group (OVX + DG-H, n = 12); DG medium-dose treatment group (OVX + DG-M, n = 12); DG low-dose treatment group (OVX + DG-L, n = 12). The rats in the EV group received estradiol valerate (1mg/tablet, Bayer China Ltd., Shanghai, China), which was dissolved in distilled water, to produce a concentration of 0.1 mg/kg body weight, which was administered daily by oral gavage. According to previous reports [42 (link),43 (link)], we use 24 mg/kg body weight/day, 48 mg/kg body weight/day and 96 mg/kg body weight/day as dosages of rats in DG-L, DG-M and DG-H, respectively. The doses of DG are equivalent to 1 time, 2 times and 4 times of the normal human dose of steroidal saponins in clinical prescription for coronary heart disease or myocardial ischemia (1.44 g/60 kg weight/day). The rats in the DG groups were administered DG (Sigma-Aldrich, Saint Louis, MO, USA, purity > 95%, dissolved in distilled water) at three dose daily by oral gavage (1 mL/100 g body weight). The rats in the SHAM and the OVX groups were administered the same volume of distilled water by oral gavage (1 mL/100 g body weight). The treatment started 1 week after surgery for 12 weeks. On the 15th day and the 3rd day before sacrifice, all of the rats received tetracycline (Sigma-Aldrich, Saint Louis, MO, USA) at 30 mg/kg body weight by intraperitoneal injection. The rats in all groups were fed standard rodent chow (Animal Center of the Fourth Military Medical University, Xi’an, China). The body weight of each rat was monitored weekly to assess the effect of the treatments.