Interrelationships of dietary protein level,aflatoxin B1 metabolism,and hepatic microsomal epoxide hydrase activity

In a continuation of studies on protein intake and aflatoxin B₁ (AFB₁) metabolism, weanling rats were fed semipurified diets containing either 20% casein or 5% casein for two weeks to determine the effect of dietary protein level on hepatic microsomal epoxide hydrase activity and AFB₁ metabolism in an effort to evaluate the role of protein intake on the formation and degradation of the reactive metabolite of AFB₁. Styrene oxide was used as substrate for epoxide hydrase since the hypothetical AFB₁ 2,3-epoxide (AFB-epox) cannot be synthesized because of its lability. Two groups of animals were fed 20% casein diets; one was fed ad libitum and the second was pair fed to the 5% casein group in order to control the effects of total feed intake. The depression of epoxide hydrase activities caused by the 5% casein diets was approximately equivalent to that previously seen with hepatic microsomal mixed function oxidase (MFO) activities with the identical protocol. Similarly, the metabolism of AFB₁ to AFQ₁ and AFM₁ was depressed by the 5% casein diets, with an increase in the production of chromatographically more polar material. The relationship of the MFO and epoxide hydrase activities to AFB₁ metabolism and formation of macromolecular adducts is discussed.