Estrogen and progesterone receptors in mammary tumors induced in rats by simultaneous administration of 17 beta-estradiol and progesterone

Abstract

Mammary tumors were promoted in male rats of the Wistar WAG strain by continuous and simultaneous administration of 17 beta-estradiol and progesterone. Tumor induction and growth were dependent on estradiol and on progesterone. Their histological features were comparable with those of human breast cancers. Hormone receptors were present in tumor cells. Estradiol receptor was found in 95% of them, at a higher level in nuclei than in cytosol. Progesterone receptor was present in 75% of tumors. In all cases, the level of androgen receptor was low.