Graduate Thesis Or Dissertation
 

Dietary protein and aflatoxin B₁ metabolism in rainbow trout (Salmo gairdneri)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gh93h3754

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  • Dietary protein intake has been observed to influence the induction of cancer in animals exposed to carcinogens, presumably by affecting the activities of enzyme systems which metabolize them. One such carcinogen is aflatoxin B₁ (AFB₁) a mold metabolite and frequent contaminant of foodstuffs. Variations in the levels of dietary proteins fed rats and rainbow trout (Salmo gairdneri) influence the induction of hepatocellular carcinoma by AFB, in these animals. The following work was undertaken to provide an explanation of these results in terms of AFB₁ in vitro metabolism. The effect of dietary casein and fish protein concentrate (FPC) levels upon the activities of potential AFB₁ metabolizing enzyme systems were studied in the rainbow trout (Salmo gairdneri). Hepatic subcellular protein and cytochrome P-450 contents, and the activities of glutathione-S-epoxide transferase (GTr) epoxide hydrase (EH) cytochrome c reductase and aldrin epoxidase (AE) enzymes were determined in trout fed varying levels of casein or FPC. In addition, the reduction of AFB₁ to aflatoxicol (AFL) and conversion to an active mutagen for Salmonella typhimurium TA 98 were examined. A prerequisite for this study was the adaptation of the Ames mutagen assay system for use with fish hepatic enzymes. Lowered hepatic GTr and AE activities and increased conversion of AFB₁ to AFL and to a microbial mutagen were noted in trout fed high protein diets relative to those fed low protein diets. Cytochrome P-450 content was observed to decrease with increasing dietary casein and increase with increasing dietary FPC. Hepatic EH activity remained constant and decreased in trout fed increasing levels of casein or FPC respectively. These changes in enzyme activity are discussed in relation to dietary influences upon AFB₁ carcinogenesis in the rainbow trout.
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