Abstract:Objective To explore the expression and significance of estrogen receptor α (ERα), ERβ, activator protein 1 (AP-1) and VEGF in rat model of endometriosis (EM). Methods Subcutaneous implantation was used to establish EM model in female rats. The rats with successful ectopic implants were served as model group (n = 28), and the normal rats served as control group (n = 10). The histopathological changes of ectopic implants were observed after four weeks. The expression levels of ERα, ERβ, AP-1 and VEGF in the endometrium and endometriosis lesions were observed by immunohistochemistry in the two groups. Results There were more glands and blood vessels in the stroma of endometriosis lesions and the endometrium of the model group. There was no statistically significant difference in ERα expression level between the endometriosis lesions of the EM model and the endometrium of the control group (P = 0.107), but its expression level in the endometrium of the model group was obviously increased compared with the control group (P < 0.01). The expression levels of ERβ, AP-1 and VEGF in the endometriosis lesions and endometrium of the EM model were obviously increased compared with those of the control group (P < 0.01), but there was no statistically significant difference between the endometriosis lesions and endometrium of the EM model. Conclusions ERα and ERβ are obviously increased in the endometrium of the EM rat model; but in the endometriosis lesions, only ERβ is significantly increased. Moreover, the expressions of AP-1 and VEGF are up-regulated in the EM model. ERβ may play a more important role than ERα in the occurrence of endometriosis.