Sister chromatid exchange induction and cell cycle inhibition by aniline and its metabolites in human fibroblasts

Abstract

Abstract Sister chromatid exchange (SCE) and cell cycle analyses in human fibroblasts were used to ascertain the relative genotoxicity and cytotoxicity of aniline and its metabolites. Fibroblasts were allowed to attach to plastic petri dishes for 4 hr and exposed in serum‐free medium for 2 hr to the following: aniline HCl (0.05–10.0 mM), acetanilide (0.1–10.0 mM), o‐hydroxyacetanilide (0.01–2.0 mM), p‐hydroxyacetanilide (0.1–10.0 mM), o‐aminophenol (0.01–0.3 mM), p‐aminophenol (0.005–0.2 mM), N‐phenylhydroxylamine (0.001–0.5 mM). Triethylenemelamine (TEM; 0.25 and 0.49 μM) was used as a positive control. The treatment medium was replaced with complete medium containing 5‐bromo‐deoxyuridine (10 μM), and cells were allowed to grow for 48 hr with Colcemid present for the final 4.5 hr. Cell cycle analyses (percentage of cells in first, second, or third division) revealed that p‐hydroxyacetanilide (10mM), p‐aminophenol (≥0.1 mM), o‐aminophenol (≥0.1 mM), N‐phenylhydroxylamine (≥ mM), and TEM (0.49 μM) inhibited cell proliferation. Cell death was seen at doses of 0.5 mM N‐phenylhydroxylamine, 0.2 mM p‐aminophenol, and 0.3 mM o‐aminophenol. Significant increases (P0.05) in SCE frequencies were found with aniline HCl, o‐aminophenol, N‐phenylhydroxylamine, and TEM. On an SCE/mmole basis at the highest concentrations examined, o‐aminophenol was 270 times more potent than aniline in inducing SCE, whereas TEM was about 390 times more potent than o‐aminophenol. Furthermore, fibroblasts treated with o‐aminophenol responded in a dose‐dependent fashion and exhibited a 2‐fold increase in SCE frequency. N‐phenylhydroxylamine induced a less clear‐cut, dose‐related increase in SCE frequency with a 1.4‐fold elevation. Only marginal increases in SCE were observed with aniline at the highest doses. Using these data, we propose that aniline may exert its tumorigenic potential in rats through the production of both genotoxic and cytotoxic metabolites.