32P-postlabelling analysis of 1,3-butadiene-induced DNA adducts in vivo and in vitro

Butadiene monoepoxide (BMO), epoxybutanediol (EBD) and diepoxybutane (DEB) are reactive metabolites of 1,3-butadiene (BD), an important industrial chemical classified as ii probable human carcinogen, The covalent interactions of these metabolites with DNA lead to the formation of DNA adducts which may induce mutations or other types of DNA damage, resulting in tumour Formation. In the present study, two pairs of diastereomeric N-1-BMO-adenine adducts were identified in the reaction of BMO with 2'-deoxyadenosine-5'-monophosphate (5'-dAMP). The major products formed by reacting EBD with 2'-deoxyguanosine-5'-monophosphate (5'-dGMP) were characterized as diastereomeric N-7-(2',3',4'-trihydroxybut-1'-yl)-5'-dGMP by UV and electrospray mass spectrometry. The formation of N-7-BMO-guanine adducts (1'-carbon, 60; 2'-carbon, 54/10(4) nucleotides) in BMO-treated DNA was about four times higher than that of N-1-BMO-adenine adducts (1'-carbon, 20; 2'-carbon, 8.7/10(4) nucleotides). However, the recovery of N-1-BMO-adenine adducts in DNA (45 +/- 5%) was two times higher than that of N-7-guanine adducts (20 +/- 4%) by P-32-postlabelling analysis. Using the P-32-postlabelling/HPLC assay, N-1-BMO-adenine, N-7-BMO-guanine and N-7-EBD-guanine adducts were detected in BMO- or DEB-treated DNA and in liver DNA of rats exposed to ED by inhalation. The amount of N-7-EBD-guanine adducts (11/10(8) nucleotides) in rat liver was about three-fold higher than N-7-BMO-guanine adducts (4.0/10(8) nucleotides). The novel finding of N-1-BMO-adenine adducts formed in vivo may contribute to the understanding of the mechanisms of BD carcinogenic action.