Influence of prostatic secretion protein on uptake of androgen‐receptor complex in prostatic cell nuclei

Prostatic secretion protein (PSP) is a major component of rat prostatic cytosol, and this protein is also found in the prostatic fluid. Purified PSP was found to inhibit the nuclear uptake of the [³H]methyltrienolone-receptor complex in vitro. Furthermore, purified PSP inhibited the binding of this androgen-receptor complex to DNA-cellulose. It is suggested that these effects of PSP may represent an intracellular control system regulating the concentration of PSP. Administration of estramustine, the dephosphorylated metabolite of the anti-cancer drug estramustine phosphate (Estracyt), to rats was found to decrease the weight of the prostate gland but to maintain the concentration of PSP, calulated as mg PSP/mg protein, at a constant level. In contrast, castration or administration of estradiol -17β valerate decreased the weight of the prostate gland as well as the concentration of PSP. These findings indicate that the mechanism of action of estramustine is at least partially different from that of estradiol-17β. Furthermore, it is suggested that estramustine may exert part of its action through is effects on the concentration of PSP.