Antimutagenicity of green tea polyphenols in the liver of transgenic medaka

We examined the ability of a mixture of the predominant green tea polyphenolic compounds (GTP) to reduce benzo[ a ]pyrene (B[ a ]P)‐induced mutations in the cII gene of the λ transgenic medaka. Fish were treated with 50 ppb B[ a ]P for 24 hr, followed by exposure to 2 ppm or 10 ppm GTP for 28 days. cII mutations in livers of fish exposed to B[ a ]P were increased significantly, 2.6‐fold above controls. In contrast, the addition of GTP significantly reduced the frequency of cII mutants by 84%, comparable to that of controls. The frequencies of mutations at G:C basepairs, mutations that are highly characteristic of B[ a ]P exposure, were elevated significantly in treated fish. By comparison, B[ a ]P‐exposed fish also treated with GTP showed reductions in these mutations, demonstrating a protective effect of GTP against B[ a ]P‐induced mutagenesis. The antioxidant mechanism of GTP possibly played an important role in the reduction of B[ a ]P mutagenicity. These results corroborate findings from rodent models, showing that the protective effects of green tea extend to different species, and suggesting that similar mechanisms of B[ a ]P mutagenesis and GTP antimutagenesis are shared among the models. These studies illustrate the utility of λ transgenic medaka for in vivo mutation analyses and suggest that this fish may be a valuable model in chemoprevention studies. Environ. Mol. Mutagen., 2005. © 2005 Wiley‐Liss, Inc.