Repeated-dose liver and gastrointestinal tract micronucleus assays for quinoline in rats

•We conducted the RDLMN assays using quinoline in young adult rats.•The MNHEPs in the quinoline-treated groups were significantly increased.•The numbers of micronucleated stomach, colon and bone marrow cells did not increase.•The RDLMN assay is useful for detecting liver carcinogens.•The RDLMN assay is capable of being incorporated into general toxicity studies. Repeated-dose liver, bone marrow, and gastrointestinal tract micronucleus assays that use young adult rats were evaluated in a collaborative study that was organized by the Japanese Environmental Mutagen Society–Mammalian Mutagenicity Study Group. A genotoxic hepatocarcinogen quinoline was orally administered to independent groups of five Crl:CD (SD) male rats at doses of 30, 60 and 120mg/kg for 14 days and at doses of 15, 30 and 60mg/kg for 28 days. After treatment, the livers were harvested and hepatocytes were isolated by collagenase treatment. The frequency of micronucleated hepatocytes (MNHEPs) increased significantly in both the 14- and 28-day repeated dose studies. However, the frequency of micronucleated cells did not increase in the bone marrow, stomach or colon cells, which were not quinoline-induced carcinogenic target organs in the rats. These results indicate that a repeated-dose liver micronucleus (RDLMN) assay using young adult rats is capable of detecting the genotoxicity of quinoline at the target organ of carcinogenicity. The protocol may also permit the integration of the genotoxic endpoint into general repeated-dose toxicity studies. Furthermore, we elucidated that conducting the micronucleus assay in multiple organs could potentially assess organ specificity.