Quantitative analysis of 4-aminobiphenyl-C8-deoxyguanosyl DNA adducts produced in vitro and in vivo using HPLC-ES-MS

Electrospray mass spectrometry (ES-MS) is a powerful tool for analysis of c arcinogen-adducted DNA. In this study, we developed a quantitative isotope dilution method for analysis of N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG -C8-4-ABP), the principal nucleoside adduct derived from enzymatic hydrolys is of 4-aminobiphenyl (4-ABP)-modified DNA. The method used column switchin g valves to perform on-line sample concentration and cleanup, which permitt ed direct analysis of enzymatic DNA hydrolysates using narrow-bore liquid c hromatography (LC), ES-MS detection was performed using a single quadrupole instrument by monitoring M+H+ and two fragment ions characteristic for dG- C8-4-ABP, along with M+H+ and a fragment ion for the deuterated internal st andard. The detection limit for dG-C8-4-ABP in DNA hydrolysates was similar to 10 pg on-column, equivalent to 0.7 dG-C8-4-ABP adducts in 10(7) normal nucleotides for a sample containing 100 mu g DNA. The method was applied to the analysis of calf thymus DNA modified ill vitro through reaction with N -hydroxy-4-ABP and of hepatic DNA isolated from mice treated ill I vivo wit h two dose levels of 4-ABP.