Gender differences of enzymatic activity and distribution of 17beta-hydroxysteroid dehydrogenase in human skin in vitro.

The interconversion of estrone (E1) and 17beta-estradiol (E2) is catalyzed by 17beta-hydroxysteroid dehydrogenase (17beta-HSD) in peripheral steroidogenic organs such as the skin. To investigate gender differences of activity and skin distribution of 17beta-HSD in human skin, enzymatic activity was measured in skin homogenates and skin horizontally sliced by 10 microm thickness in vitro. Reductive 17beta-HSD (E2 formation from E1) in female skin has a lower substrate affinity than in male skin; Km (Michaelis-Menten constant) of female and male skin is 11.8 +/- 6.5 and 2.0 +/- 2.0 microM, respectively. Female skin had a tendency to activate estrogen; Vmax (maximum rate) for E2 formation, 5.8 +/- 4.0 pmol/min/mg protein, is 1.7 times larger than E1 formation, 3.5 +/- 1.5 pmol/min/mg protein, and, on the other hand, male skin tends to deactivate estrogen; Vmax for E1 and E2 is 10.5 +/- 6.1 and 4.2 +/- 3.7 pmol/min/mg protein, respectively. The concentration of metabolite had a peak value at 80-120 microm from the skin surface. Therefore, these in vitro results suggest that the enzymatic activities of 17beta-HSDs have a gender difference in estrogen formation/metabolism and are distributed around the basement layer of the epidermis irrespective of sex. 17Beta-HSDs distributed around the basement epidermis may be effectively supplied with circulating estrogen from the papillary plexus to maintain the estrogen level in skin. This distribution pattern having a peak surrounding 100 microm from the skin surface indicates the importance for defense from noxae (e.g. detoxication) and maintenance of the internal environment (e.g. biosynthesis of hormones). Future studies should increase sample size and confirm these results by stricter statistical analysis.