Stromal 5α-reductase activity is elevated in benign prostatic hyperplasia

Abstract

The activities of 5.alpha.-reductase and 3.alpha.(.beta.)-hydroxysteroid dehydrogenase were assayed in homogenates of stroma and epithelium obtained from 3 normal, 9 hyperplastic and 2 carcinomatous human prostates. Irrespective of the normal or abnormal condition of the prostate, the localization of 5.alpha.-reductase was predominantly in stroma whereas the reductive and oxidative activities of 3.alpha.(.beta.)-hydroxysteroid dehydrogenase were more evenly divided between stroma and epithelium. The mean specific activity of 5.alpha.-reductase in hyperplastic stroma at 84.6 .+-. 13.1 (.+-. standard error of the mean) pmol 30 min-1 per mg protein was almost 3 times greater (Student''s t-test, P < 0.05) than the corresponding value in normal stroma, 31.6 .+-. 7.2 pmol mg protein per 30 min. Apparently the stroma is the primary site of conversion of testosterone to dihydrotestosterone in the human prostate owing to the prevalence in stroma of 5.alpha.-reductase, and benign prostatic hyperplasia is characterized by an increased amount of stromal 5.alpha.-reductase activity.