Nephroblastomas Induced in Ovariectomized Rats by Dimethylbenzanthracene

The effects of intragastrically administered 7,12-dimethylbenzanthracene were investigated in intact and ovariectomized 50-day-old Sprague-Dawley rats. Ovariectomy resulted in an 80% decrease in the incidence of mammary tumors after 7.5 months. On the other hand renal tumors developed between the 5th and the 8th month in 14% of the castrated animals, while not a single instance was recorded in intact rats. These tumors were histologically typical of nephroblastoma. The similarity to fetal kidney was confirmed by lack of reactivity of the newly formed tubules to both oxidative and hydrolytic enzymes normally present in differentiated epithelial cells of the nephron and in epithelial kidney tumors of adult type.