IN VITRO STUDIES OF TESTOSTERONE AND 5α-DIHYDROTESTOSTERONE BINDING IN BENIGN PROSTATIC HYPERTROPHY

Abstract

The cytosol fractions of prostatic adenoma and of the rectus abdominis muscle, together with the respective plasma samples were investigated in 13 patients in order to clarify whether or not there is an androgen receptor in human benign prostatic hypertrophy. The following methods were used: High speed ultracentrifugation in a sucrose gradient and agar gel electrophoresis at low temperature, of the 100 000 g supernatants after in vitro incubation with ³H-testosterone, ³H-5α-dihydrotestosterone, and ³H-oestradiol-17β. In parallel experiments the supernatants were heated to 45°C for 1 h before the steroid incubation. Displacement experiments with a 100–500-fold excess of various cold androgens. In the supernatants as well as in the plasma samples the total protein concentration was measured by the biuret reaction. The concentration of albumin and of immunoglobulin G (IgG) in the various biological fluids was determined by quantitative immuno diffusion. After charcoal stripping the binding of testosterone and of 5α-dihydrotestosterone was estimated quantitatively and correlated to the plasma contamination. By the methods used no physico-chemical differences in the androgen binding properties of plasma and of prostate cytosol were observed. However, in any individual cytosol a higher 5α-DHT binding than could be related to the plasma contamination was obtained. The question therefore remains open, as to whether the augmented 5α-dihydrotestosterone binding relates to a cellular increase of sex hormone binding globulin (SHBG) or to androgen receptors which do not show up clearly under the experimental conditions used.