Abstract: Objective To investigate the effects of different doses of dexamethasone (Dex) on bone mineral density (BMD) and body composition in Sprague-Dawley (SD) rats. Methods Forty female 3-month-old SD rats were divided into four groups by the doses of Dex, control group (Cont, saline), low dose group (LDG, 1mg/kg ), medium dose group (MDG, 2.5mg/kg) and high dose group (HDG, 5mg/kg). Ten rats for each group, injected intramuscularly twice a week. The BMD and body composition were measured at the beginning and 4 weeks later by DEXA densitometer. Results The body weight of Cont was increased with time, the body weight of different doses of Dex intervention groups were decreased after 1 to 4 weeks intervention when compared with the Cont. After 4 weeks intervention, the total BMD, femur BMD, total BMC, total fat mass, trunk fat mass, leg fat mass of Cont were increased while the total lean mass, trunk lean mass of Cont were decreased when compared with itself before intervention. The total BMC, femur BMD, leg lean mass, leg fat mass of LDG and MDG were lower than the cont (P＜0.05). The femur BMD, leg fat mass of LDG and MDG were lower than the HDG(P＜0.05). Conclusion The doses of 1mg/kg and 2.5mg/kg Dex have greater influence than the dose of 5 mg/kg Dex on the femur BMD and the leg composition of SD rats by intramuscular injections twice a week for 4 weeks, and can lead the femur BMD and leg fat mass decreased.

Key words: Dexamethasone, Bone mineral density, Body composition, rats, Sprague-Dawley