Androgen Receptor in Human Skin Cytosol*

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Abstract
Human skin, an accessible tissue, is an androgen target organ. We have measured the androgen-binding capacity of human skin cytosol using either 5α-[3H\dihydrotestosterone ([3H\DHT) or [3H\methyltrienolone ([3H\R-1881) as ligand. Samples were incubated for 20 h at 0 C, and dextran-coated charcoal was used to separate bound from free steroids. The androgen receptor has a high affinity for both ligands (0.23 ± 0.04 nM for [3H\DHT; 0.32 ± 0.16 nM for [3H\R-1881). Testosterone, cyproterone acetate, and, to a lesser extent, estradiol also bind this protein. Progesterone displaces R-1881 from its binding sites, whereas its 5α-reduced metabolite somewhat inhibits DHT binding. The highest binding capacity is measured in cytosol of skin from external genitalia (129.14 ± 58.0 fmol⁄g skin; n = 34); it is lower in pubic skin (21.8 ± 13 fmol⁄g skin; n = 6). There is no variation as a function of age or sex in genital skin; the higher concentrations observed in the cytosol of pubic skin of women compared to that of men are probably related to lower levels of endogenous steroids. Whereas most patients with the complete form of the testicular feminization syndrome do not have detectable concentrations of androgen receptor, one patient with apparent complete clinical androgen insensitivity had a normal androgen-binding capacity. The parity of values in genital skin from men and women, the absence of variation with age, and the presence of a cytosolic androgen receptor in some androgeninsensitive patients suggest that the androgen receptor in human skin cytosol is not regulated by androgens.