Abstract:Objective: To explore the effect mechanism of Sanlengwan (SLW) on estrogen production in ectopic endometrium of rats. Method: The rat model of endometriosis was established by surgical implant of endometrial tissue which belong to its body. Forty EMS model rats were randomly divided into five groups (n=8): model control group, three different concentration SLW groups and anastrozole group. Meanwhile, eight normal rats were used as the normal control group. All the rats were treated for 4 weeks respectively, the changes of the P450 arom and cyclooxygenase-2 protein were measured by immunohistochemical test and western blot respectively before and after treatment of SLW, and the level of secretion of estrodiol and prostaglandin E2 was also measured by ECLIA and RIA. Result: SLW can reduce the expression of P450 arom protein ,and the levels of estradiol after treatment of SLW were significantly lower than that of the model group in ectopic endometrial tissue (P<0.05); The high dose group of SLW can inhibit the expression of cyclooxygenase-2 protein and also reduce the production of prostaglandin E2 (P<0.05). Conclusion: SLW can reduce the production of estradiol in the ectopic endometrial tissue of rats, and its mechanism might be associated with inhibiting the expression of P450 arom and interruption the positive feedback loop of estradiol production.