Liver DNA bound in vivo with aflatoxin B1 as a measure of hepatocarcinoma initiation in rainbow trout.

The in vivo binding of aflatoxin B1 (AFB1) to liver DNA was measured in rainbow trout subjected to various regimens and in coho salmon to determine if binding would correlate with tumor incidence and initiation of hepatocellular carcinoma. Establishment of time-course binding parameters showed no significant difference between 4, 12, 24, or 48 hours. Doses of 5, 25, 100, and 300 micrograms AFB1/kg body weight produced an almost linear increase in binding with increasing dose. Compared to that of controls, AFB1-DNA binding was twofold lower in beta-naphthoflavone-treated trout and twentyfold lower in coho salmon. These two comparisons reflected a decrease in the effective activation and binding of AFB1, correlated with tumor incidence, and are believed to correlate with a decrease in the initiation of hepatocellular carcinoma. AFB1 binding was not significantly altered by dietary protein or cyclopropenoid fatty acids, which are thought to increase hepatocellular carcinoma incidence through promotional effects. The data were consistent with the view that in vivo binding of AFB1 to liver DNA is a measure of cancer inititation by AFB1 and correlated with the incidence of hepatocellular carcinoma in salmonid fish.