DNA binding of benzo[a]pyrene metabolites. Effects of substrate and microsomal protein concentration in vitro, dietary contaminants, and tissue differences.
The binding of reactive benzo[a]pyrene metabolites to deproteinized DNA in vitro can be drastically changed, both quantitatively and qualitatively, in vitro by changes in the substrate concentration or the substrate/P-450 ratio, and in the intact animal by starvation or substitution of a 'purified protein test diet' for the regular laboratory chow. Liver, lung, and bowel microsomes from C57BL/6N and DBA/2N mice were examined. These data demonstrate the importance of dietary contaminants or nutrition during benzo[a]pyrene tumorigenesis. The profile of DNA binding of benzo[a]pyrene metabolites is also shown to be an extremely sensitive test for detecting minute amounts of induced cytochrome P1-450 and its associated aryl hydrocarbon (benzo[a]pyrene) hydroxylase (EC 1.14.14.2) activity. A direct correlation is not necessarily observed, however, between 'aryl hydrocarbon hydroxylase activity' and the amount of benzo[a]pyrene metabolites bound covalently to DNA. 'Untreated' genetically responsive mice are shown to have greater 'control' levels of benzo[a]pyrene metabolism in their various tissues than genetically nonresponsive mice simply on the basis that responsive mice have a lower threshold for 'responsiveness' to exogenous inducers inhaled and/or ingested in their crude diet, i.e., responsive 'control' animals already have partially induced enzymes.
D000818:Animals; D001580:Benzopyrenes / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004032:Diet; D005506:Food Contamination; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008861:Microsomes / Q000378:metabolism*; D009928:Organ Specificity; D011506:Proteins / Q000378:metabolism; D013045:Species Specificity
D001580:Benzopyrenes; D011506:Proteins; D004247:DNA