QUANTITATIVE-ANALYSIS OF 1,3-BUTADIENE-INDUCED DNA-ADDUCTS IN-VIVO AND IN-VITRO USING LIQUID-CHROMATOGRAPHY ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROMETRY

1,3-Butadiene (ED) is a high volume industrial chemical which is known as a multi-site rodent carcinogen and is classified as a probable hum an carcinogen. Covalent interactions of the reactive epoxy metabolites of ED with DNA lead to the formation of DNA adducts which may cause m utations and tumor formation. In the present work, liquid chromatograp hy/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was employed for analyses of ED-induced DNA adducts in vitro and in vivo. Selected reaction monitoring (SRM) using the fragmentation of the [M + H](+) ions of the adducts to the corresponding protonated nucleobase s under collision-induced dissociation was performed. Quantitation was based on isotope dilution with C-13- and N-15-labeled internal standa rds. The methods were applied in vitro [calf thymus DNA and TK6 cell c ultures treated with epoxy metabolites of ED, 3,4-epoxy-1-butene (EB) and diepoxybutane (DEB)] and in vivo [DNA isolated from tissues of ED- exposed laboratory animals ]. Two regioisomers of N-7-EB-guanine adduc ts, N-7-(2-hydroxy-3-buten-1-yl)guanine (N-7-EB-Gua I) and N-7-(1-hydr oxy-3-buten-2-yl)guanine (N-7-EB-Gua II) and two N-3-EB-adenine isomer s, N-3-(2-hydroxy-3-buten-1-yl)adenine and N-3-( 1-hydroxy-3-buten-2-y l)adenine (N-3-EB-Ade I and II), were found in EB-exposed samples. N-7 -(2',3',4'-trihydroxybut-2-yl)guanine (N-7-THB-Gua), N-6-(2',3',4'-tri hydroxybut-1'-yl)adenine (N-6-THB-Ade), and N-3-(2',3',4'-trihydroxybu t-1'-yl)adenine (N-3-THB-Ade) were detected in DEB-treated DNA. DNA is olated from Liver and lung of rats and mice exposed to 1250 ppm ED for 2 weeks contained both regioisomers of N-7-EB-Gua and N-3-EB-Ade, as well as N-7-THB-Gua and N-6-THB-Ade. The methods developed in this wor k provide the means to study accumulation, repair and dose-response re lationships of BD-DNA adducts in vivo. Although less sensitive than ga s chromatography/electron capture negative ionization high-resolution mass spectrometry (GC/ECNI-HRMS), LC/ESI+-MS/MS in the SRM mode is ext remely useful for analysis of ED-DNA adducts, which are not amenable t o GC and derivatization owing to the presence of several adjacent pola r functional groups. Using LC/ESI+-MS/MS and isotope dilution, multipl e structurally diverse BD-DNA adducts can be analyzed simultaneously i n the same sample with minimal sample preparation. (C) 1998 John Wiley & Sons, Ltd.