Genotoxicity of furazolidone and the free form of the metabolite: 3-amino-2-oxazolidone, based on human lymphocyte micronucleus test

Abstract

The aim of this trial was to assess the genotoxic effects of the main metabolite of furazolidone (3-amino-2-oxazolidone- AOZ), which is usually protein-bound (PB-AOZ). Because PB-AOZ is not available as a tool for biomedical research, the synthetic free form of AOZ (F-AOZ) was used to challenge human lymphocytes in the genotoxic quantification test of in­duced micronuclei on human lymphocytes. The level of exposure of lymphocytes to F-AOZ was calculated by determining the residual quantity of the Bg-AOZ (from liver and muscle) by HPLC, derived from broilers fed furazolidone included at 0.11% and 0.22% in feed, and allowing a seven day withdrawal time. Then F-AOZ and furazolidone as positive genotoxic group were added at various concentrations higher than the residual level indication to the in vitro preparations diluted both in dimethyl sulfoxide (DMSO) as follows: for furazolidone (FZD) groups of 10 μM (225 mg/g), 1.0 μM (225 mg/g), 0.1 μM (22.5 mg/g), and 0.001 μM (0.225 mg/g), as well as a negative control group and positive control with DMSO 10-3 M (0.130 mg/g) and arsenic 10-3 M (0.747 mg/g), respectively; for F-AOZ 0.01 μM (1.020 mg/g); 0.102 μM; 0.0005 μM (0.051 mg/g); and 0.0001 μM (0.001 mg/g) were tested, having the same controls groups as for FZD. Results show that furazolidone from 10.0 μM through 0.1 μM possesses a well defined genotoxic effect. Association frequency, relative risk and ANOVA test showed a statistically significant effect vs the negative control group (P = 0.001; P = 0.03 and P = 0.04, respectively). For F-AOZ the same statistical tests showed that only 0.01 μM was capable of inducing a genotoxic effect. These results suggest that furazolidone as parent compound is potentially capable of inducing genotoxicity in consumers. In contrast, only the highest concentration of F-AOZ was shown to induce a similar effect. Yet this concentration is well above the expected residual concentration after a 7-day withdrawal period. These results do not support the use of furazolidone in humans as it is now accepted and reveals that F-AOZ is a considerably lower hazard to public health than the parent compound. Yet, lack of evidence of the effect of bound-AOZ in a similar setting precludes further comparisons, but these results suggest that it seems unlikely that PB-AOZ is a real risk to public health. Further studies are warranted.