Detection of 1, N2-propanodeoxyguanosine adducts as potential endogenous DNA lesions in rodent and human tissues

Our previous study (R.G. Nath and F-L. Chung; Proc. Natl. Acad. Sci. USA, 91: 7491-7495, 1994), using a 32P postlabeling method combined with high-performance liquid chromatography specifically developed for exocyclic adducts, has shown that acrolein- and crotonaldehyde-derived 1,N2-propanodeoxyguanosine adducts (AdG and CdG, respectively) are present in the liver DNA from humans and rodents without carcinogen treatment. Those findings raised important questions regarding their role as potential endogenous DNA lesions in carcinogenesis. In this study, using a similar assay, we examined a variety of tissues from untreated rats and mice (lung, kidney, brain, breast, prostate, colon, skin, and leukocytes) and detected AdG and CdG in the DNA of these tissues. More significantly, we also obtained evidence for the presence of these adducts in the DNA of human leukocytes and mammary glands. The identities of these adducts were verified by comigration of 3', 5' -bisphosphates of the 32P-labeled adduct from DNA with the synthetic standards in a reversed-phased high-performance liquid chromatography. Additional proof of identities was provided by enzymatic conversion of AdG and CdG 3',5' -bisphosphates to the corresponding 5'-monophosphates, followed by comigration with their synthetic standards. The estimated ranges of total AdG and CdG modifications in DNA of various tissues were from 0.10 to 1.60 mumol/mol guanine for humans, based on the recoveries of external standards. This study demonstrated the ubiquity of these adducts in various tissues, suggesting their potential role as endogeneous DNA lesions in rodents and humans.