In Vivo Uptake and Metabolism of Testosterone by the Skin and Other Tissues of the Rat

The study investigated the uptake and metabolism of radioactively labeled testosterone in the skin, plasma, and other tissues of adult castrated rats. The skin showed similar uptake and retention of radioactivity to classical androgen target organs, but the composition of radioactivity in the skin differed significantly from that in the accessory glands. In the skin, testosterone was the major unconjugated steroid, while 5α-dihydrotestosterone (5α-DHT) and other metabolites were present in smaller quantities. In contrast, 5α-DHT was the predominant steroid in the ventral prostates. The plasma contained mostly conjugated or polar forms of radioactivity, but all steroids found in the skin were also present in plasma. The findings suggest that 5α-DHT may not be as important for the skin as it is for the prostate in rats, indicating that testosterone and possibly other androgens could play a more significant role in the skin's androgenic mechanism.