Abstract: Objective This study investigated the role of estrogen receptors in the metabolism of temporomandibular cartilage by applying different concentration of 17β-estradiol (17β-E2) to ovariectomized (OVX) rats.Methods 1.The female SD rats were randomly assigned to the control group,sham group,OVX group and hormone replacement therapy group . Different concentration of 17β-E2 were injected timely and delayed. 2. The change of estrogen level was verified by testing the shape and mature index of vaginal epithelium exfoliated cells, then the ERα and ERβ in rat condylar cartilage were tested by using Western-blot and Real-time PCR analysis subsequently. Results 1)The maure index of vaginal epithelium exfoliated cells of OVX rats was 180/12/8, indicating low levels of estrogen in vivo(P＜0.05). 2) ER mRNA could maintain at the normal level when 5×102μg/kg of 17β-E2 were supplemented immediately. Yet this was not the case when 17β-E2 were given delayed. 3. Both 50μg/kg and 5×103μg/kg of 17β-E2 administration can suppress the expression of ER, either in protein or mRNA level, and this inhibitory effect is more obvious in 5×103μg/kg group(P＜0.05).Conclusion The biological effects of OVX rats of ER depend on normal physiological concentration and accurate period of estrogen secretion.

Key words: Condylar cartilage, Estrogen, Estrogen Receptor