[Studies on the androgen-binding proteins in human benign prostatic hypertrophy].

Androgen-binding proteins in the cytosol of human benign prostatic hypertrophic tissue were studied with 3H-dihydrotestosterone (DHT) and 3H-methyltrienolone (R 1881) as ligands. In the prostatic cytosol, saturable binding proteins with high affinity to 3H-DHT or 3H-R1881 were found by Scatchard analysis. The dissociation constant (Kd) for 3H-DHT was 9.4 X 10(-10)M, and the maximum number of binding sites (B max) was 55 fmoles/mg protein; the Kd for 3H-R1881 was 5.1 X 10(-9)M, and B max was 25.5 fmoles/mg protein. Competitive binding assay for each binding protein with various non-labeled steroids, demonstrated a specificity for DHT or R1881. The binding of prostatic cytosol and 3H-DHT was eluted by Sephadex G-200 column chromatography in 2 places, one in the void volume and one near the IgG fraction. The binding with 3H-R1881 was eluted in the void volume, the elution near the IgG fraction being very small, which suggests a non-specific binding. The binding of prostatic cytosol and 3H-DHT increased with increase in the concentration of Ca2+ or Mg2+ (0-12 mM), but the binding with 3H-R1881 decreased conversely. This change was studied with Sephadex G-200 column chromatography; the binding with 3H-DHT showed a decrease of the peak in the void volume and marked increase of the peak near the IgG fraction with increase in the concentration of both ions, whereas the binding with 3H-R1881 only showed a decrease of the peak in the void volume. Ca2+ had a greater influence than Mg2+ on the change of these bindings. These results indicate a change of binding protein due to ionic action, suggesting also the possibility of the presence of a substance in the cytosol which changes the properties of the binding protein dependent on Ca2+.