Null effect of dietary Aroclor 1254 on hepatocellular carcinoma incidence in rainbow trout (Salmo gairdneri) exposed to aflatoxin B1 as embryos

Abstract

Four lots of 200 rainbow trout embryos were exposed to 200 ml solutions of aqueous 0.5 ppm aflatoxin B1 (AFB1) for 1 hr, and 4 lots of 200 rainbow trout embryos were sham-treated for 1 hr. After hatching and swimup, 100 fry from each group were selected for a feeding trial. Two groups of AFB1-treated and 2 groups of sham-treated fry were fed a control diet, while corresponding groups of AFB1-treated and sham-treated fry were fed the control diet plus 100 ppm Aroclor 1254 for 1 year. Samples were taken at 9 and 12 mon to monitor tumor incidence, Aroclor 1254 accumulation and histopathology. At the end of 12 mon, the liver cancer incidences in the combined AFB1-treated, control diet groups and the AFB1-treated, Aroclor 1254 diet groups were essentially the same. 65.8% and 63.9%, respectively. One trout in the sham-control, Aroclor 1254 diet group had a single liver cancer, but the sham-control, control diet group had none. The Aroclor 1254 fed groups had significantly higher liver to body weight ratios at 12 noon but not at 9 mon. Levels of accumulated Aroclor 1254 were similar to those reported previously, approximately 75 ppm on a whole fish basis at 12 mon. Glycogen depletion of hepatocytes and splenic hyperemia were the only tissue changes induced by Aroclor 1254.