Objective To investigate the effect of estrogen on heat shock protein（HSP） 70 expression in rat masseter muscle. Methods Sixty twelve-week-old female Sprague-Dawley rats were randomly divided into three groups: Sham surgery group（control group）, ovariectomy group（OVX group）, ovariectomy with estradiol valerate replacement treatment group（OVX/EV group）. Half of the animals were sacrificed at 4 and 8 weeks respectively, then the masseter muscle was removed. Immunohistochemistry（IHC） method was employed to study the HSP70 expression in masseter muscle. Results Compared to control group and OVX/EV group, the expression of HSP70 was significantly lower at 8 weeks in OVX group（P＜0.05）. There were no significantly difference between the HSP70 expression of control group and that of OVX/EV group. Conclusion Estrogen may affect HSP70 expression in rat masseter muscle, and estrogen replacement therapy may prevent HSP70 reduction.
