The uptake of two androgen substrates by cultured human gingival fibroblasts in response to minocycline and metabolic studies using a cell-free system

The uptake of two androgen substrates by cultured fibroblasts and the anabolic response of homogenates of cultured gingival fibroblasts to minocycline were investigated. Monolayer cultures of confluent fibroblasts were incubated with [14C]testosterone/[14C]4-androstenedione for timed intervals in the presence or absence of optimal concentrations of minocycline. The intracellular uptake of androgens was quantified by radio-isotope counts on cell digests. Confluent gingival fibroblasts were homogenized by snap freezing/rapid thawing and duplicate incubations were made in phosphate-buffered saline (pH 6.5) with radiolabelled androgens, in the presence or absence of minocycline, for 24 h. At the end of the incubation period the buffer was extracted for radioactive metabolites, analysed and quantified with a radio-isotope scanner. There were 30% increases in the uptake of androgen substrates in the presence of minocycline (n=3; p<0.01; one-way ANOVA). With the metabolic studies there were 2–3-fold increases in the formation of dihydrotestosterone from [14C]testosterone and [14C]4-androstenedione, respectively (n=4; p<0.001; one-way ANOVA), and 4-fold/2-fold increases in the formation of 4-androstenedione/testosterone from these substrates (n=4; p<0.001) in response to an optimal concentration of 20 μg/ml of minocycline, compared with control incubations. The presence of minocycline in the incubate significantly increased the activity of the steroid-metabolizing enzymes. This increase might result from increased intracellular availability of steroid substrate and enhanced metabolic activity. Homogenates of cultured gingival fibroblasts are a useful model for studying the anabolic potential of minocycline in gingiva, using C19 steroid substrates.