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.</p