ANALYSIS OF THE MALONDIALDEHYDE-2'-DEOXYGUANOSINE ADDUCT IN RAT-LIVERDNA BY GAS-CHROMATOGRAPHY ELECTRON-CAPTURE NEGATIVE CHEMICAL-IONIZATION MASS-SPECTROMETRY

Malondialdehyde (MDA), a product of lipid peroxidation, causes mutatio ns in bacterial and mammalian cells and cancer in rats. MDA reacts wit h deoxynucleosides in vitro and the monomeric adduct of MDA with deoxy guanosine (M(1)G-dR) is the major adduct formed. We have developed a s ensitive analytical method to characterize and quantify M(1)G-dR from biological matrices using gas chromatogrphy/electron capture negative chemical ionization mass spectrometry (GC/ECNCI MS). Reduction of M(1) G-dR with sodium borohydride produced a dihydro derivative (H-2-M(1)G- dR). This more stable analog had improved high-performance liquid chro matographic characteristics which facilitated its isolation from biolo gical fluids. H-2-M(1)G-dR was converted to a monopentafluorobenzyl de rivative with simultaneous depurination; it was then converted to the corresponding t-butyldimethylsilyl derivative and analyzed by GC/ECNCI MS. (H-2(2))H-2-M(1)G was used as internal standard. Quantitative ana lysis was carried out using selected ion monitoring of m/z 302 and m/z 304 where the limit of detection was 10 pg (30 fmol) injected on-colu mn. The level of M(1)G-dR in normal rat liver was 5.2 +/- 0.2 modified bases per 10(7) bases (n = 6 rats).