Interrelationships of dietary protein level, aflatoxin B 1 metabolism, and hepatic microsomal epoxide hydrase activity

Abstract

In a continuation of studies on protein intake and aflatoxin B 1 (AFB 1) 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 AFB 1 metabolism in an effort to evaluate the role of protein intake on the formation and degradation of the reactive metabolite of AFB 1. Styrene oxide was used as substrate for epoxide hydrase since the hypothetical AFB 1 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 AFB 1 to AFQ 1 and AFM 1 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 AFB 1 metabolism and formation of macromolecular adducts is discussed.