Inhibitory effect of Aroclor 1254 on aflatoxin-initiated carcinogenesis in rainbow trout and mutagenesis using a Salmonella/trout hepatic activation system

Abstract

Duplicate lots of 140 rainbow trout ( Salmo gairdneri) were fed either control diet (CD) or 100 ppm Aroclor 1254 (a polychlorinated biphenyl—PCB) for 3 mth followed by initiation of liver carcinomas with 20 ppb dietary aflatoxin B 1 (AFB 1) for 2 wk. At 8 and 12 mth after AFB 1 treatment, fish were sampled and tumor incidence determined. Trout that were prefed PCB showed a 45% inhibition in tumor incidence at 12 mth, when compared to those prefed CD. Throughout the experiment fish were sampled to determine the time relationship of PCB bioaccumulation. A rapid uptake of PCB into total body fat was seen, with concentration of 594 ppm at the time of AFB 1 exposure. Liver benzo[ a]pyrehe monooxygenase (B[ a]PM) activity was also induced at the time AFB 1 exposure began. The Ames mutagenesis assay was used to determine the effects of in vitro Aroclor 1254 on AFB 1-induced mutagenesis using a trout liver preparation. A PCB dose-related inhibition was observed with a 67% inhibition at the highest dose tested (500 μg Aroclor 1254/plate). Proposed mechanisms of the inhibition of AFB 1-induced carcinogenesis/mutagenesis are discussed.