Author Masumura K, Horiguchi M, Nishikawa A, Umemura T, Kanki K, Kanke Y, Nohmi T.
Title Low dose genotoxicity of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in gpt delta transgenic mice.
Journal Mutat Res
Abstract Although humans are chronically exposed to most environmental chemicals at low doses, genotoxicity assays with rodents are usually performed at high doses with short treatment period. To investigate the dose-response of genotoxicity at lower doses, gpt delta transgenic mice were fed a diet containing 300, 30 or 3 parts per million (ppm) of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) for 12 weeks and the gpt mutations in the liver were analyzed. In addition, the mice were continuously fed a diet containing MeIQx at a dose of 300 ppm for 78 weeks to examine the effect of a long-term treatment. In the mice treated for 12 weeks, the gpt mutant frequencies (MFs) were 8.6-, 2.3- and 1.2-fold higher than the control level at the doses of 300, 30 and 3 ppm, respectively. G:C to T:A transversion was the most predominant type of mutations and the fold increases in the specific MF of G:C to T:A were 58.2, 4.4 and 1.7 above the control at the three doses, respectively. The increases in the whole gpt and specific MFs at 3 ppm were not statistically significant. In the mice treated with 300 ppm of MeIQx for 78 weeks, the gpt MF was about 20 times higher than that of the untreated mice fed a control diet for 78 weeks, which was about two times higher than that of the untreated mice at 12 weeks. These results suggest that no obvious genotoxic effects can be detectable at the dose of MeIQx at 3 ppm in the liver and a longer treatment substantially enhances the genotoxicity. Factors constituting the practical threshold dose are discussed.
Volume 541(1-2)
Pages 91-102
Published 2003-11-10
DOI 10.1016/s1383-5718(03)00186-4
PII S1383571803001864
PMID 14568298
MeSH Animals Bacterial Proteins / genetics* DNA Damage DNA Replication / drug effects Dose-Response Relationship, Drug Escherichia coli Proteins Mice Mice, Inbred C57BL Mice, Transgenic Mutagens / toxicity* Mutation Pentosyltransferases Proteins* Quinoxalines / toxicity*
IF 2.463
Times Cited 24
Mice RBRC00159