Factors affecting the reproducibility of androgen receptor determinations in human prostate

Several factors affecting the reproducibility of androgen receptor assays in the human prostate gland have been identified. Experiments in the presence of proteolytic inhibitors such as PMSF, leupeptin and aprotinin resulted in no change in the estimates of androgen receptors. The androgen binding was also unaffected by the concentrations of endogenous steroids in the tissue. Although the receptor assay was reliable down to protein concentrations of about 5 g/l, at lower concentrations the reliability of the method was significantly reduced. Similarly, tissue storage at -25 degrees C drastically lowered the binding capacity of the prostatic tissue extracts to 50% of initial receptor content over a period of 3 months. The high degree of correlation between receptor levels in the stroma and epithelium suggests that the binding in the total gland will not be drastically affected by the proportion of stroma and epithelium it contains. Following the widely practised 2-h extraction of the nucleus with 0.6 mol/l KCl buffer, a highly significant non-extractable binding component remained. Analysis of data by the single-point assay produced results comparable to those obtained by standard Scatchard analysis and seemed reliable so long as careful quality control was employed.