Inhibitory effects of Serenoa repens on the kinetic of pig prostatic microsomal 5alpha-reductase activity.

The pathogenesis of benign prostatic hyperplasia is linked to the accumulation of dihydrotestosterone (DHT), the active form of testosterone (T), in prostatic tissue. We have defined characteristics of 5alpha-reductase enzyme which catalyzes the conversion of T into DHT in prostatic microsomes of growing pigs. Peaks for the 5alpha-reductase activity were found at pH 5.5 and 8.0, which indicates the presence of both type 1 and type 2 isozymes. Kinetic parameters of porcine 5alpha-reductase in the presence of Serenoa repens extracts revealed uncompetitive, noncompetitive, and mixed types of inhibitions. Our results show the inhibitory action of S. repens on prostate porcine microsomal 5alpha-reductase activity.