Assessment of the in vivo genotoxicity of cadmium chloride, chloroform, and d,l-menthol as coded test chemicals using the alkaline comet assay

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) international validation study of in vivo rat alkaline comet assays, we examined cadmium chloride, chloroform, and d,l-menthol under blind conditions as coded chemicals in the liver and stomach of Sprague-Dawley rats after 3 days of administration. Cadmium chloride showed equivocal responses in the liver and stomach, supporting previous reports of its poor mutagenic potential and non-carcinogenic effects in these organs. Treatment with chloroform, which is a non-genotoxic carcinogen, did not induce DNA damage in the liver or stomach. Some histopathological changes, such as necrosis and degeneration, were observed in the liver; however, they did not affect the comet assay results. d,l-Menthol, a non-genotoxic non-carcinogen, did not induce liver or stomach DNA damage. These results indicate that the comet assay can reflect genotoxic properties under blind conditions.