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. / Graduation date: 1978
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27117 |
| Date | 28 April 1978 |
| Creators | Stott, William T. |
| Contributors | Sinnhuber, Russell O. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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