Abstract

PIP: This study investigates the carcinogenic effects of castration, stilbestrol, progesterone, testosterone, and combined estrogen and progesterone treatment on Lister strain rats. While castration seems to reduce the number of sarcomas in the cervico-vaginal tract when induced by 9,10-dimethyl-1,2-benzanthracene (DMBA), estrogens in doses sufficient to enlarge to normal size the castrate uterus inhibit the formation of sarcomas in intact rats, and fail to promote that in castrate animals. On the other hand, stilbestrol in doses insufficient to restore to normal the atrophy of the uterus, promotes and accelerates the formation of sarcomas and of epithelial tumors of the cervico-vaginal tract in castrate but not in intact rats. Progesterone in intact rats retards the induction of sarcomas but promotes papillomas of the cervix and vagina. Combined with estrogens, progesterone restores the rate of sarcoma formation to the level of intact rats. In both intact and in castrated rats testosterone seems to lengthen the induction period of sarcomas or to increase the formation of epithelial tumors; these effects are reduced when testosterone is combined with stilbestrol. Cholesterol increases the formation of sarcomas and epithelial tumors in castrate rats. Epithelial tumors as well as sarcomas arise at about the same time and rate in castrate animals given intermittently stilbestrol per os. The rate of tumor formation is greater than that in intact animals without additional treatments. The carcinogenic effects of estrogens, progesterone, cholesterol and testosterone are not correlated with the effect of the same substances on the normal tissues of the uterus, vaginal stroma, or other target organs.