Nuclear binding of androgens and acid phosphatase activity in prostatic tumors of Nb rats

Abstract

A transplantable prostatic adenocarcinoma derived from the dorsal lobe of the prostate gland of an Nb rat was analyzed for the concentration of nuclear androgen-binding sites and the presence of acid phosphatase activity. When extracts of nuclei from normal prostatic tissue were labelled with [1,2- 3H]dihydrotestosterone in the absence and presence of competitor, two types of specific binding were observed: type 1 was characterized by an association constant ( K a) of 6 · 10 7 M −1 and involved a molecule that was excluded from Sephadex G-200; type 2 was characterized by a K a of 3 · 10 8 M −1 and depended on a binding component that was retained by Sephadex G-200. Nuclei from androgen-stimulated tumors contained reduced concentrations of both androgen-binding components, whereas nuclei from autonomous tumors had only a trace amount og type 1 sites and were entirely devoid of type 2 sites. In all tumors the acid phosphatase activity per mg of protein was markedly elevated. Relative to normal, the activity of this enzyme was 140% and 350% higher in androgen-stimulated and autonomous tumors, respectively. These findings indicate that prostatic tumors are characterized by a decrease in nuclear androgen-binding, and an increase in specific activity of acid phosphatase, and also that such changes are more pronounced in autonomous than in androgen-stimulated tumors.