Biochemical study of testosterone in skin: in vivo and in vitro metabolism of testosterone in rat skin

In vitro and in vivo testosterone metabolism was studied using rat skin. The in vitro stoichiometric studies strongly suggested the existence in the skin of 5a-reductase and other enzymes involved in testosterone metabolism. The predominant metabolites were 5adihydrotestosterone, androstandiol and 6.4-androstenedione. The rate of testosterone metabolism in vitro was higher in preputial skin than in dorsal skin. The main metabolites were androstandiol and 6 4-androstenedione in vivo whereas dihydrotestosterone and androstandiol were predominant in vitro. .6.4-Pathway is considered to be more active in vivo in adults than in newborns. The difference in the in vivo uptake increase of testosterone-3H after castration suggests the possible existence in the organs and skin areas of androgen pools of different sizes. The in vivo uptake and metabolism of testosterone were examined in the nuclei of newborn rats. Dihydrotestosterone and androstandiol detected in the nuclei of preputial skin, dorsal skin and liver were 42.8%, 24.3% and 27.8%, of total radioactivity incorporated into the respective organs. The liver incorporated only a small amount of radioactivity compared with the skin.