ANALYSIS OF 1,N-2-ETHENOGUANINE AND 7,9-TETRAHYDRO-7-HYDROXY-9-OXOIMIDAZO[1,2-A]PURINE IN DNA TREATED WITH 2-CHLOROOXIRANE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ELECTROSPRAY MASS-SPECTROMETRY AND COMPARISON OF AMOUNTS TO OTHER DNA-ADDUCTS

High performance liquid chromatography (HPLC)/electrospray mass spectr ometry methods were developed for the analysis of 1/N-2-etheno(epsilon )guanine (Gua) and 7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine (HO-ethanoGua) [the cyclized form of N-2-(2-oxoethyl)Gua] and its deox yribose derivative in DNA. Evidence was provided for the formation of the latter adduct in DNA treated with 2-chlorooxirane, the reactive pr oduct formed from the carcinogen vinyl chloride. Measured levels of HO -ethanoGua and HO-ethanodeoxyguanosine were similar, although the assa y for the deoxyribosyl derivative has some technical advantages. 3,N-4 -epsilon-Deoxycytidine was also estimated in 2-chlorooxirane-treated D NA using HPLC with fluorescence detection. Levels of all known adducts formed from vinyl chloride have now been estimated in DNA treated wit h 2-chlorooxirane and vary in the order N-7-(2-oxoethyl)Gua >> 1,N-6-e psilon-adenine > HO-ethanoGua > N-2,3-epsilon-Gua > 3,N-4-epsilon-cyto sine > 1,N-2-epsilon-Gua. Although in vivo adduct levels may not paral lel these due to differential stability and rates of repair, analyses of the adducts in DNA treated with 2-chlorooxirane provide a basis for consideration of the biological effects of these adducts.