Dependency of Estramustine Binding Protein (EMBP) from Rat Prostate to Endogeneous Androgen

Abstract

In this study, we investigated the dependency of estramustine binding protein (EMBP) from rat prostate on endogenous androgen. The EMBP content of the dorsolateral prostate markedly decreased 14 days after castration and increased again after the cessation of the weekly subcutaneous administration of 2 mg of Estradiol-17 beta valerate, in accordance with the recovery of prostate weight and serum testosterone concentration. This result clearly demonstrated that EMBP, which was present in very small quantities in the dorsolateral prostate, had a dependency on endogenous androgen as well as on the ventral prostate EMBP. We investigated the changes in prostate weights, EMBP concentration and serum testosterone level throughout life. The ventral prostate weight began to increase rapidly at 7 weeks of age and showed a broad peak from 11 to 14 weeks of age and then gradually decreased. On the other hand, the dorsolateral prostate weight began to increase rapidly at 7 weeks of age and continued to increase very gradually even after 10 weeks of age. There was a remarkable difference in the changes in EMBP concentration between the ventral prostate and the dorsolateral prostate. In the ventral prostate, EMBP concentration increased markedly from 4 to 9 week of age. Thereafter it continued to increase very gradually. On the other hand, in the case of the dorsolateral prostate, EMBP demonstrated higher and fluctuating concentration from 4 to 15 weeks of age. After 16 weeks of age, EMBP showed lower and stable concentration, although the weight of dorsolateral prostate showed gradual increase. These results suggested that there exist, beside androgens, some factors that participated in the regulation of growth and functional metabolism in the dorsolateral prostate after 16 weeks of age.