In vitro assay of androgen binding by human prostate

The in vitro binding of 5α-dihydrotestosterone by a “cytosol” fraction of human pathological tissue was investigated, and compared with binding by the rat prostate, an androgen-responsive mouse mammary tumour, and some androgen-unresponsive control tissues. Androgen-binding levels in the human control tissues were higher than those in the rat and mouse, and were not lower than androgen-binding levels in many prostatic specimens from untreated patients. Estrogen therapy and/or orchiectomy appeared to result in higher binding levels. The steroid specificity of binding in the human prostatic tissue appeared closer to that of sex hormone binding globulin than to that of the androgen receptor in the rat prostate. It was concluded that the assay used was not sufficiently specific to distinguish androgen binding by sex hormone binding globulin from that by an intracellular prostatic androgen receptor.