Objective       To investigate the therapeutic mechanism of modified Da Qiqi decoction (MDQD

a traditional herbal prescription）for endometriosis.       Methods       The endometriosis model was established in 37 female SD rats and identified with pathological observation. After 3 weeks

they were randomly divided into high dose MDQD group (n=9

5.072 g/kg)

low dose MDQD group (n=9

1.268 g/kg)

gestrinone group (n=9

0.5 mg/kg)

and model group (n=10)

and another 10 rats with sham-operation served as control. Corresponding age

nts or normal saline at same volume were given by intragastral administration for 3 weeks. The levels of E

2

and PGE

2

in the serum and ectopic endometrial tissues were measured by ECLIA and ELISA. The expression of P450 and COX-2 at protein and mRNA levels in the ectopic endometria were determined by immunohistochemistry and RT-PCR.       Results       Compared with model group

high dose MDQD treatment resulted in significant decline in the E

2

and PGE

2

levels in the serum and endometrial tissues

and decreased expression of P450 and COX-2 at protein and mRNA levels (P0.01). There was no significant difference in above parameters between the high dose MDQD group and gestrinone group (P0.05).       Conclusion       MDQD reduces the contents of P450

COX-2 and PGE

2

in endometriosis rats

which inhibits the growth of ectopic endometria through suppressing estrogenic generation to decrease the level of E

2

in serum and local lesions.