IN-VITRO REACTIONS OF 2-CYANOETHYLENE OXIDE WITH CALF THYMUS DNA

Acrylonitrile oxide (CEO) is a direct-acting mutagen and the postulate d proximate carcinogenic form of acrylonitrile (AN). We have studied t he reactions of CEO with 2'-deoxyribonucleosides and in vitro with cal f thymus DNA at pH 7.0 - 7.5 and 37-degrees-C for 3 h. Reaction of CEO with dAdo gave 2 adducts, N6-(2-hydroxy-2-carboxyethyl)-dAdo (N6-HOCE -dAdo) (2% yield) and 1,N6-etheno-dAdo (epsilon-dAdo) (11%); reaction with dCyd resulted in the isolation of 3-HOCE-dUrd (22%); reaction wit h dGuo gave 7-(2-oxoethyl)-Gua (7-OXE-Gua) (31%) and reaction with dTh d yielded 3-OXE-dThd (3%). Structural elucidation of adducts was accom plished by ultraviolet spectroscopy, high-field proton NMR spectroscop y and mass spectrometry. Structural confirmation was provided by an ac curate mass measurement technique where diagnostic ions in the electro n impact mass spectra of trimethylsilyl derivatives were measured to w ithin 0.0007 atomic mass units. The facile Dimroth rearrangement of 1- HOCE-dAdo to N6-HOCE-dAdo and hydrolytic deamination of a dcyd adduct to 3-HOCE-dUrd is postulated to be catalyzed by the hydroxyl group on the 3-carbon side chain of the adduct. Reaction of CEO with calf thymu s DNA yielded (nmol/mg DNA) N6-HOCE-dAdo (2); Epsilon-dAdo (11); 3-HOC E-dUrd (80); 7-OXE-Gua (110) and 3-OXE-dThd (1). Thus CEO, like its me tabolic precursor AN, directly alkylates DNA in vitro but at a much mo re rapid rate.