Genotoxicity of Zearalenone, an Estrogenic Mycotoxin: DNA Adduct Formation in Female Mouse Tissues

Zearalenone is a non-steroidal estrogenic mycotoxin produced by several species of Fusarium which colonize maize, barley, oats, wheat and sorghum and have been implicated in numerous mycotoxicoses in farm animals, especially pigs. In a NTP mouse study a dose-related incidence of hepatocellular adenomas was seen in female mice. A limited number of genotoxicity assays have been conducted with zearalenone. Zearalenone was found to be negative in the Salmonella typhimurium assay. It was also negative in a eukaryotic cell mutation assay with Saccharomyces cerevisae. However, zearalenone and its estrogenic metabolites showed a positive DNA damaging effect in recombination tests with Bacillus subtilis. In this study DNA adducts in female mice and rat treated i.p or orally with zearalenone were determined using a 32P-postlabeling method. Several DNA adducts (12-15) were found in the kidney and liver of female mice treated with a single dose of zearalenone (2 mg/kg i.p. or orally). The total DNA adduct levels reached 114 +/- 37 and 1393 +/- 324 adducts/10(9) nucleotides respectively in kidney and liver after i.p. treatment and 548 +/- 50 adducts/10(9) nucleotides in liver after oral treatment. In mice ovary DNA adducts appeared only after repeated doses (1 mg/kg body wt on days 1, 5, 7, 9 and 10). The total DNA adducts after 10 days in this organ were 17 +/- 5 adducts/10(9) nucleotides. Some adducts were common to all organs. Others were specific to an organ. In contrast, no DNA adducts could be detected in rat organs after i.p. treatment. These results confirm the genotoxicity of zearalenone and its ability to induce hepatocellular adenomas, rather than tumours of genital organs, in mice.