OBJECTIVE To study the changes in inflammatory factors caused by prostatitis.METHODS SD rats were castrated under sterile conditions.E2 0.25 mg· kg-1+ T 0.25,0.5 and 1.0 mg· kg-1 were given sc for 30 d,respectively.Serum samples were taken and levels of E2,T and dihydrotestosterone (DHT) were detected by ELISA.Pathological changes of prostate tissue were observed by HE staining.The expressions of tumor necrosis factor-alpha (TNF-α),cyclooxygenase-2 (COX-2) and macrophage inflammatory protein 1alpha (MIP-1α) in prostate were detected by immunohistochemistry.RESLULTS ELISA detection showed that E2 levels were significantly increased [(80±7) ng· L-1,P＜0.01] in E2 0.25 mg· kg-1 group and that T levels were significantly decreased [111 ±6 vs (111 ±5) nmol· L-1,P＜0.05]in E20.25 mg ·kg-1 and E2+T 0.25 mg·kg-1 groups compared with the sham-operated group.E2 was significantly increased [(80±7) ng· L-1,P＜0.01] in E20.25 mg· kg-1 groups compared with the castrated control.The sham and castrated control showed normal glandular epithelium without leukocyte infiltration.In E2 0.25 mg·kg-1 group,extensive infiltration of inflammatory cells was found in the glandular lumens,suggesting the occurrence of chronic prostatitis.In each E2+T groups,fewer inflammatory cells were noted in the stroma around glands.The expressions of TNF-m COX-2 and MIP-1α in sham group were negative or low,while those of castrated control and E2 0.25 mg· kg-1 groups were high,especially in E2 0.25 mg· kg-1 group.The expressions of TNF-α,COX-2 and MIP-1α in each E2+T group were significantly decreased.CONCLUSION Testosterone can inhibit prostatitis and the expression of inflammatory factors,such as TNF-α,COX-2 and MIP-1 α,in castrated SD rats initiated by estrogen.