The purpose of this study is to reveal the effect of estrogen-inducing SOD activity on the endometrium of domestic rabbits. Researchers measured Superoxide Dismutase (SOD) activity to investigate the reason of occurrence of popular uterine adenocarcinoma in rabbits in estradiol-17β-stimulated endometrium epithelial cell culture. Then, we also examined the distribution of cells expressing Estrogen Receptor α (ERα)-like Immunoreactivites (ERα-like-IR) in the uterus prone to developing adenocarcinoma. The addition of estradiol-17β to the primary culture of endometrial epithelial cells obviously decreased SOD activity. Moreover, the areas of endometrium in which uterine glands were confined in control rabbits and notably larger in rabbits with glandular hyperplasia of the uterus compared in normal dog uterus that the occurrence of uterine adenocarcinoma is rare. ERα-like-IR cells were found in all proliferating glands in rabbits with hyperplasia.