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Carcinogenesis Advance Access published online on July 6, 2005
Carcinogenesis, doi:10.1093/carcin/bgi177
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© The Author 2005. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oupjournals.org
Received April 30, 2005
Revised June 14, 2005
Accepted June 28, 2005

CARCINOGENESIS

Quantitative determination of urinary N7-ethylguanine in smokers and nonsmokers using an isotope dilution liquid chromatography/tandem mass spectrometry with on-line analyte enrichment

Mu-Rong Chao 1, Chien-Jen Wang 2, Louis W. Chang 2, and Chiung-Wen Hu 3*

1 Department of Occupational Safety and Health, Chung Shan Medical University, No.110, Sec.1, Chien-Kuo N Road, Taichung, Taiwan (402)
2 Division of Environmental Health and Occupational Medicine, National Health Research Institutes, 100 Shih-Chuan 1st Road, Kaohsiung, Taiwan
3 Department of Public Health, Chung Shan Medical University, No.110, Sec.1, Chien-Kuo N Road, Taichung, Taiwan (402)

* To whom correspondence should be addressed.
Chiung-Wen Hu, E-mail: windyhu{at}csmu.edu.tw


  Abstract

Previous studies demonstrated the presence of unknown direct acting ethylating agents arising from cigarette smoke. We hypothesized that such agents would also lead to ethylation of guanine in DNA followed by depurination/repair and excretion of N7-ethylguanine (N7-EtG) in urine. In this study, a highly specific and sensitive liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method was firstly developed for measuring the urinary N7-EtG. With the use of an isotope internal standard (15N5-N7-EtG) and on-line enrichment techniques, the detection limit of this method was estimated as 0.59 pg/ml (0.33 pmol) on-column. This method was then applied to measure urinary samples obtained from 35 nonsmokers and 32 smokers with dietary control. The results showed that the mean urinary levels of N7-EtG were 85.5 ± 105 and 28.1 ± 19.4 pg/mg creatinine for smokers and nonsmokers, respectively. Smokers had about three times higher level of N7-EtG than nonsmokers (P < 0.005). It was further noted that the urinary level of N7-EtG was significantly associated with the cotinine for smokers (r = 0.49, P < 0.005). Taken together, this is the first study demonstrated the presence of N7-EtG in urine, and cigarette smoke was highly responsible for the increased urinary excretion of N7-EtG. This non-invasive measurement of urinary N7-EtG would be useful for the surveillance of ethylating agent exposure and its associated cancer risk in the future.


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Clinical-Scale High-Throughput Analysis of Urinary 8-Oxo-7,8-Dihydro-2'-Deoxyguanosine by Isotope-Dilution Liquid Chromatography-Tandem Mass Spectrometry with On-Line Solid-Phase Extraction
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[Abstract] [Full Text] [PDF]


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