Detection of 1,N²-propanodeoxyguanosine adducts in DNA of Fischer 344 rats by an adapted ³²P-post-labeling technique after per os application of crotonaldehyde

Crotonaldehyde is an important industrial chemical to which humans and animals are ubiquitously exposed. The main intake occurs via food, tobacco smoke and possibly also via beverages. Estimation of intake via the different routes is difficult since the data available on exposure are inconsistent. Crotonaldehyde is genotoxic, mutagenic and carcinogenic and forms 1,N²-propanodeoxyguanosine adducts as the main DNA adducts. We have developed a ³²P-post-labeling method for these adducts based on nuclease P1 enrichment and polyethyleneimine-cellulose TLC which allows reliable detection with a detection limit of 3 adducts/10⁹ nucleotides, a labeling efficiency of 80-90% and a recovery of 38%. Using this method we found crotonaldehyde adducts in different organs of Fischer 344 rats after a single gavage of high doses of 300 and 200 mg/kg body wt in the range 0.3-3.2 ± 0.4 adducts/10⁸ nucleotides and after repeated gavage of low doses of 10 and 1 mg/kg body wt (five times a week for 6 weeks) 6.2 ± 0.2 and 2.0 ± 0.4 adducts/10⁸ nucleotides, but not in untreated animals nor in calf thymus DNA not treated with crotonaldehyde. In contrast to our results, Chung and co-workers found adducts in tissue of untreated Fischer 344 rats. This discrepancy could depend on the different methods used but also on differences in exposure of the animals via food or due to animal housing, etc.