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

In an attempt to understand dietary protein effects upon aflatoxin B1-induced liver cancer in rainbow trout, the activities of several suspected aflatoxin B1 metabolizing enzyme systems were studied relative to protein intake. Fish fed diets containing 32 percent, 52 percent and 62 percent fish protein concentrate (FPC) were examined for hepatic cytochrome P-450 content and in vitro cytochrome c reductase, glutathione-S-epoxide transferase (GTr), epoxide hydrase (EH) and aldrin epoxidase (AE) activity. In addition, aflatoxin B1 conversion to aflatoxicol (AFL) was examined. A direct correlation was observed between increased FPC intake and cytochrome P-450 content and AFL production, with increases of 14 percent and 41 percent respectively. With increased FPC intake, decreases in EH (15 percent), GRr (20 percent), cytochrome c reductase (13 percent) and AE (50 percent) activities were noted. These findings are discussed in relation to AFB feeding trials reported earlier.