A macromolecular component which specifically binds tritium-labeled-dihydrotestosterone is present in cultured amniotic fluid cells. The androgen-binding complex is characterized by a 3.6S sedimentation coefficient, an apparent dissociation constant of 1 nmol/L, a mean binding capacity of 243 +/- 140 fmol/mg of DNA, and a specificity for testosterone and dihydrotestosterone. Similar properties have been reported for the androgen receptor of the fetal genital skin fibroblast, which suggests that the tritium-labeled-dihydrotestosterone-binding component in amniotic fluid cells is the androgen receptor. Amniotic fluid cell monolayers incubated with serum-free medium containing testosterone are able to transform testosterone into dihydrotestosterone. The 5 alpha-reduced product has been characterized by thin-layer chromatography and capillary column gas-liquid chromatography. Androgen receptors and 5 alpha-reductase activity are expressed in amniotic fluid cells. The prenatal diagnosis of 5 alpha-reductase deficiency or complete androgen insensitivity syndrome (testicular feminization) is thus theoretically possible and obviously prenatal testing would be indicated in the family at high risk.

We previously suggested [Steroids33, (1979) 3; Steroids37, (1981) 6] that cultured genital skin fibroblasts should prove useful for screening of potential antiandrogens in human and living target cells. “Serenoa repens” lipidic extract (S.R.E.) was recently reported (Br. J. Pharmacoi., in press) to inhibit androgen action in animals. The present investigation was designed to study the antiandrogenicity of this compound in human cells: we therefore analyzed the effects of S.R.E. on the intracellular conversion of testosterone (T) to 5α-reduced derivatives, and we investigated interaction of S.R.E. with the intracellular androgen-receptor complex. Since the chemical structure of the active component of S.R.E. is still unknown, results are expressed in U/ml (one unit is defined as the amount of S.R.E. required to inhibit 50% of the specific binding (IC50) of [3H]1881 to rat prostate cytosol).

Reduction of dihydrotestosterone into 5 alpha-androstan-3 alpha, 17 beta diol by 3 alpha hydroxysteroid dehydrogenase was studied in human cultured skin fibroblasts. Characterization of the 3 alpha diol was performed by gas-liquid chromatography coupled with mass spectrometry. Sex skin fibroblasts enzyme has the same Km (9.10 X 10(-6) M) as that of non sex skin fibroblasts (8.75 X 10(-6) M). On the other hand, reduction of DHT is 3 times higher in sex skin fibroblasts (Vmax = 223.9) than in non sex skin fibroblasts (Vmax = 87.9). Thus, human culturel fibroblasts appear again to be an useful tool for the study of a key-enzyme of androgen metabolism in target cells.

In men, parallel variations in urinary 3 alpha 5 alpha androstane 17 beta diol with the amount of sex skin fibroblast DHT receptors rise the question of a relationship of 3 ketosteroid reductase activity and specific DHT binding. To test this hypothesis, we measured 3 alpha 5 alpha androstane 17 beta diol biosynthesis in cultured sex skin fibroblasts, in the presence of high amounts of cyproterone acetate which competes with DHT for its receptor: when 95% of DHT is displaced by cyproterone acetate, the 3 keto steroid reductase activity remains unchanged. These results suggest that the relationship of 3-keto-steroid reductase activity and androgen receptors is unlikely.

Human skin may be considered as a target organ for androgens, since events characteristic of androgen action have been described in this tissue, as well as in cultured human skin fibroblasts. The culture of human skin fibroblasts gives the opportunity to work on living cells, under controlled conditions, in a renewable material from a single skin biopsy. Using this method, we showed the presence od DHT-receptors in the human fetus and we studied the ontogenesis of androgen receptors in relation to sexual differentiation. In the neonatal period, the physiological T rise was not concurrent with a variation in sex skin androgen receptors. The evolution of DHT binding during puberty is now under investigation. These data suggest that the androgen receptor is not modulated by plasma androgens. Androgen receptor determination is of value in defining the biochemical defects involved in partial and complete androgen insensitivity syndrome (twenty-six cases in our study). In idiopathic hirsutism, DHT binding is used to detect an eventual local hypersensitivity. Fibroblast cultures have also been shown to be an excellent model for the screening of compounds which might block the expression of androgen action by competing for the androgen receptors. Cultured skin fibroblasts are a valuable model for the study of androgen and antiandrogen action in human skin.