Abstract
Alkylpurines are liberated from alkylated DNA by glycosylase repair enzymes and, in most cases, excreted in urine without further metabolism. This phenomenon forms the basis of noninvasive methods to measure DNA alkylation in vivo. In the case of methyl adducts, such as 7-methylguanine (7-MeGua), natural backgrounds exist due to RNA turnover. However, deuterated (d3) methylating agents or precursors give rise to d3-7-MeGua and d3-3-methyladenine (3-MeAde), which can be readily quantitated using gas chromatography-mass spectrometry (GC-MS). A deuterated probe drug, such as d6-aminopyrine, can be used to measure endogenous nitrosation levels in experimental animals. In contrast, for higher alkyl homologues of alkylpurines, natural backgrounds are low or nonexistent and can be directly measured by GC-MS using stable isotope labeled internal standards. For example, increased levels of urinary 3-ethyladenine were observed in cigarette smokers. Due to recent advances in analytical methodology, notably immunoaffinity cleanup of urine, measurements of excreted DNA adducts can be used in studies in human populations exposed to low levels of alkylating carcinogens.
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Selected References
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- Craddock V. M., Magee P. N. Effect of administration of the carcinogen dimethylnitrosamine on urinary 7-methylguanine. Biochem J. 1967 Aug;104(2):435–440. doi: 10.1042/bj1040435. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Farmer P. B., Parry A., Franke H., Schmid J. Lack of detectable DNA alkylation for bromhexine in man. Arzneimittelforschung. 1988 Sep;38(9):1351–1354. [PubMed] [Google Scholar]
- Farmer P. B., Shuker E. G., Bird I. DNA and protein adducts as indicators of in vivo methylation by nitrosatable drugs. Carcinogenesis. 1986 Jan;7(1):49–52. doi: 10.1093/carcin/7.1.49. [DOI] [PubMed] [Google Scholar]
- Friesen M. D., Garren L., Prevost V., Shuker D. E. Isolation of urinary 3-methyladenine using immunoaffinity columns prior to determination by low-resolution gas chromatography-mass spectrometry. Chem Res Toxicol. 1991 Jan-Feb;4(1):102–106. doi: 10.1021/tx00019a014. [DOI] [PubMed] [Google Scholar]
- Gombar C. T., Zubroff J., Strahan G. D., Magee P. N. Measurement of 7-methylguanine as an estimate of the amount of dimethylnitrosamine formed following administration of aminopyrine and nitrite to rats. Cancer Res. 1983 Nov;43(11):5077–5080. [PubMed] [Google Scholar]
- Karran P., Lindahl T. Cellular defence mechanisms against alkylating agents. Cancer Surv. 1985;4(3):583–599. [PubMed] [Google Scholar]
- Lijinsky W., Loo J., Ross A. E. Mechanism of alkylation of nucleic acids by nitrosodimethylamine. Nature. 1968 Jun 22;218(5147):1174–1175. doi: 10.1038/2181174b0. [DOI] [PubMed] [Google Scholar]
- Nagasawa H. T., Shirota F. N., Mizuno N. S. The mechanism of alkylation of DNA by 5-(3-methyl-1-triazeno)imidazole-4-carboxamide (MIC), a metabolite of DIC (NSC-45388). Non-involvement of diazomethane. Chem Biol Interact. 1974 Jun;8(6):403–413. doi: 10.1016/0009-2797(74)90046-5. [DOI] [PubMed] [Google Scholar]
- Shuker D. E., Farmer P. B. Relevance of urinary DNA adducts as markers of carcinogen exposure. Chem Res Toxicol. 1992 Jul-Aug;5(4):450–460. doi: 10.1021/tx00028a001. [DOI] [PubMed] [Google Scholar]
- Süssmuth R., Haerlin R., Lingens F. The mode of action of N-methyl-N'-nitro-N-nitrosoguanidine in mutagenesis. VII. The transfer of the methyl group of N-methyl-N'-nitro-N-nitrosoguanidine. Biochim Biophys Acta. 1972 May 10;269(2):276–286. [PubMed] [Google Scholar]