In vitro metabolism of testosterone in the rat prostate: influence of aging

The in vitro metabolism of labelled testosterone has been studied in the ventral prostate of young (2 months) and old (15 and 22 months) male rats. It has been found that the prostate of 2-month old animals converts testosterone into dihydrotestosterone (5-alpha-androstane-17-beta-ol-3-one, DHT) and into the diols (5-alpha-androstane-3-alpha,-17-beta-diol and 5-alpha-androstane-3-beta,17-beta-diol) with considerable yields. The prostate of young animals is also able to convert testosterone into delta-4-androstenedione (delta-4-A), 5-alpha-androstanedione (5-alpha-A) and androsterone (A); however, the amount of these metabolites are lower than those of DHT and the diols. Aging induces major alterations in the prostatic metabolism of testosterone. In particular, a progressive and significant decrease in the formation of DHT and of the diols has been found in animals of 15 and 22 months of age. Advancing age induces, on the contrary, a progressive and significant increase of the formation of delta-4-A. The total amounts of 5-alpha-reduced metabolites of the 17-keto series (5-alpha-A + A) are higher at 15 and 22 months than at 2 months of age. This increase appears to result from an enhanced formation of 5-alpha-A at 15 months, and of A at 22 months. The present data show that aging exerts important effects on the metabolism of testosterone in the ventral prostate of the rat. The results may help explaining why the old rat does not develop spontaneously the syndrome of benign prostatic hypertrophy (BPH), as it occurs in other species (dogs and humans).