Protective effect of green tea against benzo[a]pyrene-induced mutations in the liver of Big Blue transgenic mice.

We assessed the ability of green tea to protect against benzo[a]pyrene (B[a]P)-induced mutations in the liver of lacI transgenic male C57BL/6 Big Blue mice. The mice were given a 2% Japanese green tea hot water extract as their sole source of drinking water for 10 weeks. After 7 weeks, they received a total dose of 150 mg/kg B[a]P. Treatment with B[a]P resulted in a two-fold higher lacI mutant frequency than the untreated controls (8.6+/-0.8 x 10(-5) versus 4.0+/-0.7 x 10(-5), P=0.01). B[a]P increased the frequency of its characteristic mutation (GC-->TA transversions) nearly five-fold, from 0.75 x 10(-5) to 3.7 x 10(-5). In mice treated with green tea, the induced B[a]P mutant frequency decreased by 63%, while GC-->TA transversions were reduced by 54%. Thus, we report evidence that green tea extract significantly suppressed B[a]P-induced mutation by lowering its specific transversion mutation in the lacI transgene in vivo. Further studies will address the correlation between the modulation of metabolic enzymes and the protection against induced mutation by green tea.