Aflatoxin-DNA adduct formation in chronically dosed rats fed a choline-deficient diet

Abstract

Nutritional modulation of male Fischer rats by a cholinedeficient/methionine-low diet dramatically increases hepatocarcinogenesis and reduces time to first tumors induced by aflatoxin B₁ (AFB₁) The effect of this diet on hepatic aflatoxin-DNA adduct burden in male Fischer rats dosed with a carcinogenic regimen of AFB₁ was examined in this study. After 3 weeks of ingestion of a choline-deficient/ methionine-low diet or control semi-purified diet, rats were administered a carcinogenic regimen of 25 µg [³H]AFB₃ for 5 days a week over 2 weeks. Six choline-deficient and four control diet rats were killed 2 h after each dose, and liver DNA isolated. In addition, hepatic DNA was isolated from animals 1, 2, 3, and 11 days after the last [³H]AFB₁ administration. At all time points HPLC analysis of aflatoxin-DNA adducts was performed to confirm radiometric determinations of DNA binding levels. No significant quantitative differences in AFB₁-DNA adduct formation between the dietary groups were observed following the first exposure to [³H]AFB₁; however, total aflatoxin-DNA adduct levels in the cholinedeficient animals were significantly increased during the multiple dose schedule. When total aflatoxin-DNA adduct levels were integrated over the 10 day dose period, a 41% increase in adduct burden was determined for the cholinedeficient animals. While this increase in DNA damage is consistent with the hypothesis that DNA damage is related to tumor outcome, the biochemical basis for this effect still needs to be elucidated.