Analysis of the malondialdehyde-2'-deoxyguanosine adduct pyrimidopurinone in human leukocyte DNA by gas chromatography electron capture negative chemical ionization mass spectrometry

A method is described for the assay of the major malondialdehyde-deoxyguanosine adduct (M(1)G) based on immunoaffinity purification and gas chromatography/electron capture/negative chemical ionization/mass spectrometry. A stable isotope of M(1)G-deoxyribose ([H-2(2)]M(1)G-dR) was used as an internal standard. Recovery of internal standard throughout the entire assay procedure was similar to 40%. The assay showed a linear response over a range of 10-1000 pg of M(1)G-dR and was verified by analysis of a synthetic, M(1)G-containing oligomer. The limit of detection in biological samples was 100 fmol/sample, corresponding to 3 adducts/10(8) bases for 1 mg of DNA. DNA was isolated from the blood of 10 healthy human donors, and M(1)G levels were measured. A mean value of 6.2 +/- 1.2 adducts/10(8) bases was obtained, with no obvious differences based on age or cigarette smoking. A small, but statistically significant difference was observed between the levels in females (5.1 +/- 0.4 adducts/10(8) bases) and males (6.7 +/- 1.1 adducts/10(8) bases). The presence of M(1)G in leukocyte DNA was further verified by analysis using liquid chromatography/electrospray ionization mass spectrometry.