No abstract

The influence of dietary caffeine on the genotoxicity of the cooked food mutagen 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx) was evaluated using the host-mediated assay in mice. For four weeks, BALB/c mice were fed a purified diet with or without caffeine (0.01% wt/wt in the diet). In the host-mediated assay, Salmonella typhimurium TA98 was given intravenously immediately before an oral dose of MeIQx (1.5 mg/kg body wt). After one hour, the mice were killed, the Salmonellae were recovered from the liver, and the number of mutants (his+ revertants) were determined. Consumption of caffeine led to a 47% reduction in the number of mutants induced by MeIQx (p < 0.001). Subsequent in vitro experiments using S. typhimurium TA98 revealed that the capacity of hepatic S-9 fractions from the caffeine-fed mice to covert MeIQx to an active mutagen was reduced by approximately 35%. This effect was not attributable to caffeine in the S-9 preparation. These data suggest that consumption of caffeine modifies MeIQx mutagenicity by altering the spectrum of enzymes involved in its activation.

No abstract

The abilities of dietary fibre (wheat bran) or fat (olive oil) to modify the genotoxicity of radiolabelled MeIQ were evaluated in mice using in vivo and in vitro bacterial mutation assays. Bran reduced genotoxicity by restricting uptake of MeIQ from the gut lumen. In contrast, feeding mice a high fat diet led to increased hepatic conversion of MeIQ to an active genotoxin.