Evaluation of the use of cyproterone acetate competition to distinguish between high-affinity binding of [ 3H]-dihydrotestosterone to human prostate cytosol receptors and to sex hormone-binding globulin

Abstract

From preliminary experiments, it was concluded that cyproterone acetate (CA) was the most satisfactory of several anti-androgens investigated in distinguishing between high-affinity binding of [ 3H]-5α-dihydrotestosterone to rat ventral prostate cytosol and to human serum, using a simple incubation technique followed by removal of free steroid by Dextran-coated charcoal. Rat prostate cytosol (androgen receptor) binding of [ 3H]-DHT was almost eliminated by concentrations of CA which affected human serum binding to a relatively slight, though unfortunately variable, extent. The total, high-affinity, and CA-inhibitable binding of [ 3H]-DHT by prostatic cytosol of a number of patients with benign prostatic hypertrophy and prostatic carcinoma was investigated. In the untreated patients and in some patients treated by orchidectomy and/or estrogens, the total and CA-inhibitable high affinity binding of [ 3H]-DHT were correlated with the endocrine status of the patient as determined by the serum testosterone level and the high affinity [ 3H]-DHT binding capacity of the serum (equivalent to sex-hormone binding globulin (SHBG)). It was concluded that the use of cyproterone acetate to distinguish between [ 3H]-DHT binding to the androgen receptor and serum components in human prostate cytosol permits a semi-quantitative evaluation of the amounts of these two components.