Dihydrotestosterone stimulates 5 alpha-reductase activity in pubic skin fibroblasts

In vivo, the 5 alpha-reduction of testosterone (T) to dihydrotestosterone (DHT) is androgen dependent in pubic skin but not in the skin of the external genitalia. The aim of the present study was to determine whether pubic skin fibroblasts (PSF) had retained this androgen dependency. PSF were prepared from explants of skin from normal subjects (four men, three women) and three patients with complete form of the testicular feminization syndrome. Culture medium containing 5% fetal calf serum and DHT was added 24 h after subculture (day 1) and renewed every other day. 5 alpha-Reductase was assayed on day 4 or day 8 by incubation of intact cell monolayers with [3H]T (2 nM), extraction of the medium, and chromatography of the metabolites; DNA was assayed in the cell pellets; 5 alpha-reductase was expressed as fmol/micrograms DNA . h. Controls were untreated plates from the same subcultures. DHT had no effect on cell DNA, whereas it resulted in a dose-dependent increase in 5 alpha-reductase activity. In seven PSF strains tested, DHT (10(-7) M) increased 5 alpha-reductase activity 2- to 4-fold over the control levels. This effect was abolished by the simultaneous addition of cyproterone acetate (2 X 10(-6) M) and was not observed in PSF from testicular feminization syndrome patients, suggesting that it was indeed mediated via the androgen receptor. T but not estradiol or cortisol also increased 5 alpha-reductase activity in PSF. The effect of androgens was suppressed by protein synthesis inhibitors. These data provide strong evidence that PSF respond to androgens via a receptor mediated mechanism, and that 5 alpha-reductase can be used as a marker of androgen action in pubic skin in vitro as well as in vivo.