Dissociation of the 5 alpha-reductase activity from the specific dihydrotestosterone binding activity in cultured human fibroblasts

Four fibroblast lines (F1-4) were established from abdominal (F1 and F2) and vulvar (F3 and F4) skin samples obtained from women who underwent delivery. The concentration of dihydrotestosterone (DHT) binding sites was measured along with the maximum velocity for the formation of DHT from testosterone in fibroblasts from each cell line. The concentration of DHT binding sites (fmoles/mg protein) was 12.8 +/- 1.1 for F1, 12.3 +/- 1.0 for F2, 14.7 +/- 1.3 for F3 and 13.4 +/- 1.1 for F4 (mean +/- S.D. of two determinations). The respective values for the maximum velocity for the formation of DHT from testosterone (pmoles DHT formed/mg protein/h) were 8.40 +/- 0.64, 21.5 +/- 1.69, 11.8 +/- 0.85, and 31.0 +/- 2.26 (mean +/- S.D. of two determinations). These results, which demonstrate a wide diversity among values for the maximum velocity for the formation of DHT from testosterone while values for the concentration of DHT binding sites in these fibroblasts are uniform, suggest a lack of correlation between these two activities of fibroblasts.