title: Dietary caffeine reduces the genotoxicity of MeIQx in the host-mediated assay in mice.
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.
authors.affiliation: Department of Microbiology, BIBRA International, Carshalton, Surrey, United Kingdom.
authors.forename: A J
authors.initials: AJ
authors.lastname: Alldrick
authors.forename: W E
authors.initials: WE
authors.lastname: Brennan-Craddock
authors.forename: I R
authors.initials: IR
authors.lastname: Rowland
mesh_terms: D000818:Animals; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D002273:Carcinogens / Q000009:adverse effects / Q000037:antagonists & inhibitors*; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D008807:Mice, Inbred BALB C; D011810:Quinoxalines / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D012486:Salmonella typhimurium
chemical_list: D002273:Carcinogens; D011810:Quinoxalines; D002110:Caffeine; C036990:2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline; D003577:Cytochrome P-450 Enzyme System