Investigation of covalent aflatoxin B1-DNA adducts formed in vivo in rainbow trout (Salmo gairdneri) embryos and liver

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Abstract
The formation of covalent aflatoxin-DNA adducts has been studied in embryo and yearling stages of the rainbow trout ( Salmo gairdneri ). A linear relationship was found between the amount of aflatoxin B 1 (AFB 1 absorbed into 21-day-old eggs and the level of covalent modification of embryo DNA after exposure to 0.25 to 0.5 p.p.m. aqueous solutions of AFB 1 for 1 h; higher concentrations resulted in absorption of a greater proportion of AFB 1 . The principal covalent product, identified after acid and enzymatic hydrolysis of isolated embryo DNA, was chromatographically identical to 2,3-dihydro-2-(N 7 -guanyl)-3-hydroxy aflatoxin B 1 . Additional AFB 1 derivatives which were present are believed to he formed by chemical transformation of this product in DNA producing an aflatoxin-formamidopyrimidine adduct and the metabolic activation of other aflatoxin metabolites, such as aflatoxin M 1 and aflatoxin P 1 . Although the eggs were exposed to AFB 1 for a short time, covalent modification of DNA was evident over an extended period. The highest level of covalent products was present at approximately 24 h after exposure to 0.5 p.p.m. AFB 1 . Ninety-six hours later, this level had decreased slight ly; however, the distribution of covalent adducts had changed: formamidopyrimidine adducts now represented up to 50% of the hydrolyzed aflatoxin derivatives. A similar pattern of covalent aflatoxin derivatives was found in the liver DNA of yearling trout 10 h after the administration of 0.3 mg/kg AFB 1