Autoradiographic Studies of 3H‐estramustine in the Rat Ventral Prostate

Abstract

The alkylating agent 3H-estramustine [an antineoplastic drug] was administered to castrated male rats and found to accumulate in the epithelium of the ventral prostate 5 and 20 min following i.v. administration, as judged from autoradiography. Four hours after i.v. injection of this isotope, the radioactivity was recovered in the secretion of the prostatic lobuli. A preferential accumulation of radioactivity in prostatic secretion was also observed 2 h after i.m. administration of 3H-estramustine to intact or castrated rats. In contrast, 3H-estradiol and 3H-testosterone, which were also taken up by the ventral prostatic epithelium, were not recovered in prostatic secretion. 3H-Estramustine is apparently secreted from the prostatic cells into the lumina of the prostatic lobuli. A recently detected estramustine-binding protein in rat ventral prostate may be involved in this process and the present finding may be of relevance in the understanding of the mechanism of action of the chemotherapeutic agent Estracyt (estramustine phosphate) used in the treatment of advanced [human] prostatic carcinoma.