R 1881 binding receptor and DHT concentrations in human prostatic cytosol were assayed in surgically removed prostatic tissues of benign prostatic hyperplasia (BPH) and of the normal prostate. The normal prostates were obtained from totally cystectomized male patients with bladder cancer.
Cytosols were incubated with 0.25-8.0 nM (6 points) of 3H-R 1881 in the presence or absence of excess radioinert R 1881 at 4°C for 20 hours, thereafter treated with 0.5% dextran coated charcoal. Specific bindings were analysed in the form of scatchard plot analysis. Cytosol DHT levels were determined by radioimmunoassay reported previously.
Steroid specificity studies revealed that R 1881 binding receptor was inhibited not only by androgens but also by progesterone, however, an addition of 1000 fold excess triamcinolone acetonide (TCA) reduced the inhibition by progesterone. As R 1881-receptor complex was eluted at the void volume of sephacryl S-200 chromatography, the receptor was considered to be 8-9S protein.
Cytosol DHT levels were 35.5±13.6 pg/mg cytosol protein in BPH and 18.9 ±7.1 pg/mg protein in the normal prostates, showing a significantly higher value in the former (p<0.01). Kd and NBS of R 1881 receptor in BPH were 0.73 ±0.21 nM and 30.1± 9.0 fmol/mg cytosol protein and those in normal prostate were 0.68±0.28 nM, 10.2± 4.2 fmol/mg protein, respectively. NBS were also higher in BPH compared to the normal prostate (p<0.001). Moreover, DHT levels (y) and NBS (x) showed a significant correlation (y=0.631 X + 15.764, r=0.506). It was considered that both methods might posess almost equal ability to clarify the androgen dependency of prostatic tissues.
