P-32-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 che mical classified as ii probable human carcinogen, The covalent interactions of these metabolites with DNA lead to the formation of DNA adducts which m ay induce mutations or other types of DNA damage, resulting in tumour Forma tion. In the present study, two pairs of diastereomeric N-1-BMO-adenine add ucts were identified in the reaction of BMO with 2'-deoxyadenosine-5'-monop hosphate (5'-dAMP). The major products formed by reacting EBD with 2'-deoxy guanosine-5'-monophosphate (5'-dGMP) were characterized as diastereomeric N -7-(2',3',4'-trihydroxybut-1'-yl)-5'-dGMP by UV and electrospray mass spect rometry. 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) nucle otides). 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-a denine, N-7-BMO-guanine and N-7-EBD-guanine adducts were detected in BMO- o r 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 contribu te to the understanding of the mechanisms of BD carcinogenic action.