OBJECTIVETo establish an appropriate animal model of uterine leiomyoma and to understand the pathogenesis of this disease.

METHODSMature female rats were intramuscularly injected with estradiol benzoate at 200 μg or 300 μg twice a week. After injection for 8 or 10 weeks, the rats were sacrificed. We measured the serum levels of estrogen (E(2)) and progesterone (P), evaluated ER and PR expression, and calculated the leiomyoma forming rate and mortality of the rats. Histological changes were compared between rat uterine leiomyoma and human uterine leiomyoma with HE staining. The optimal dose and duration of E(2) for induction of uterine leiomyoma in rat were determined.

RESULTSIn the rats treated with estradiol benzoate 200 μg for 8 weeks ìn the serum E(2) level increased significantly (P<0.01). Uterine nodules were visible in some of the tested rats. Based on the pathohistological Results , the uterine leiomyoma developed in the treated rats demonstrated similar features as in human uterine leiomyoma. The expressions of ER and PR were increased in the leiomyoma tissues.

CONCLUSIONThe rat model of uterine leiomyoma can be established by intramuscular injection of estradiol benzoate at 200 μg twice per week for 8 weeks, with similar features as those of human uterine leiomyoma. The high concentrations of ER and PR in uterine tissue might be related with the development of uterine leiomyoma in animal.