The effects of dietary corn oil on the metabolism and mutagenic activation on N-nitrosodimethylamine (DMN) by hepatic microsomes from male and female rats.

Microsomes from male and female rats fed a diet containing 10% corn oil metabolized N-nitrosodimethylamine (DMN) more rapidly than microsomes from rats fed a similar diet devoid of corn oil. The daily administration of phenobarbital for 4 days prior to harvesting the microsomes resulted in significant induction of the Vmax for N-demethylation of DMN in rats fed the fat-free diet but resulted in no induction (females) or suppression (males) of this enzyme in rats fed the diet containing corn oil. Using concentrations of DMN ranging from 12 to 100 mM, microsomes from rats fed the high fat diet activated DMN to produce mutagenesis in S. typhimurium (TA100) more rapidly than those from rats fed the fat-free diet. Phenobarbital administration induced this activation more effectively in rats fed the corn oil diet than in rats fed the fat-free diet. Phenobarbital induces DMN N-demethylation in rats fed both fat-free and 10% corn oil diets when the DMN concentration is above 10 mM and explains, at least in part, this enhanced mutagenic activation.