Activity of 3β-hydroxysteroid dehydrogenase Δ4–5 isomerase in the human skin

The activity of 3β-hydroxysteroid dehydrogenase Δ4–5 isomerase (3β-HSD) was assayed in various tissues microdissected from the freeze-dried human skin of 13 subjects. The sebaceous gland possessed the highest activity of 3β-HSD in the skin, while the apocrine sweat gland showed only one fourth of that activity. The vellus hair follicle showed nearly one half of the activity of the sebaceous gland, whereas the terminal hair follicle exhibited much lower activity. The activity of the epidermis and of the dermis were negligible. Incubation of fresh whole skin of the forehead with 7α-3H-DHA and subsequent isolation of various tissues revealed that the metabolites identified in the sebaceous gland were androstanedione and androstenedione, whereas testosterone and/or dihydrotestosterone were not detected.