Human genital skin fibroblasts were used to study aromatase activity by analysing the [3H]H2O released as [1β-3H]androstenedione is converted to oestrone. 4-Hydroxyandrostenedione was shown to be a competitive inhibitor of this aromatase activity, the concentration of inhibitor producing 50% inhibition being 1·29 nmol/l. Dexamethasone stimulated the enzyme complex in a dose-dependent manner with half-maximal stimulation at 11·5 nmol/l. A peak of induction occurred after 16 h of preincubation. Measurement of aromatase activity in normal cell strains provided a normal range for the Michaelis–Menten constant (K m) and the maximum velocity (V max) of 6·72±0·54 nmol/l and 215·3±33·9 fmol/mg protein per h (means ± s.e.m., n = 20) respectively. K m values obtained for partial and complete androgen insensitivity syndrome (PAIS and CAIS) patient cell strains were all within the normal range. The mean Vmax±s.e.m. in cell strains from patients with PAIS (n = 13) and CAIS (n = 11) were 127·4±19·2 and 54·8±19·3 fmol/mg protein per h respectively. V max values for patients with CAIS were significantly (P < 0·001) lower than normal subjects. This suggests that aromatase expression in genital skin fibroblasts is androgen-dependent.
Journal of Endocrinology (1990) 127, 177–183