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A NEW LC-MS/MS METHOD FOR THE DETECTION AND QUANTIFICATION OF ENDOGENOUS AND VINYL CHLORIDE INDUCED 7-(2-0XOETHYL)GUANINE IN SPRAGUE DAWLEY MALE RATS
Citation:
Mutlu, E., Y. Jeong, L. B. Collins, A. L. Ham, P. Upton, D. W. WINSETT, P. A. EVANSKY, AND J. A. SWENBERG. A NEW LC-MS/MS METHOD FOR THE DETECTION AND QUANTIFICATION OF ENDOGENOUS AND VINYL CHLORIDE INDUCED 7-(2-0XOETHYL)GUANINE IN SPRAGUE DAWLEY MALE RATS. CHEMICAL RESEARCH IN TOXICOLOGY. American Chemical Society, Washington, DC, 25(2):391-9, (2012).
Impact/Purpose:
Here, we report a new sensitive LC-MSIMS method to analyze the major DNA adduct formed by VC, 7-(2-oxoethylguanine) (7-0EG).
Description:
Vinyl chloride (VC) is an industrial chemical that is known to be carcinogenic to animals and humans. VC primarily induces hepatic angiosarcomas following high exposures (≥50 ppm). VC is also found in Superfund sites at ppb concentrations as a result of microbial metabolism of trichloroethylene and perchloroethylene. Here, we report a new sensitive LC-MSIMS method to analyze the major DNA adduct formed by VC, 7-(2-oxoethylguanine) (7-0EG). We used this method to analyze tissue DNA from both adult and weanling rats exposed to 1100 ppm [13C2]-VC for 5 days. After neutral thermal hydrolysis, 7-OEG was derivatized with O-t-butyl hydroxylamine to an oxime adduct, followed by LC-MSIMS analysis. The limit of detection was 1 fmol and the limit of quantitation was 1.5 fmol on the column. The use of stable isotope VC allowed us to demonstrate for the first time that endogenous 7-0EG was present in tissue DNA. We hypothesized that endogenous 7-OEG was formed from lipid peroxidation and demonstrated the formation of [13C2]-7-0EG from the reaction of calf thymus DNA with [13C18]-ethyl linoleate (EtLa) under peroxidizing conditions. The concentrations of endogenous 7-0EG in liver, lung, kidney, spleen, testis and brain DNA from adult and weanling rats typically ranged from 1.0-10.0 adducts per 106 guanine. The exogenous 7-0EG in liver DNA from adult rats exposed to 1100 ppm [13C2]-VC for 5 days was 104.0 ± 23.0 adducts per 106 guanine (n=4), while concentrations in other tissues ranged from 1.0-39.0 adducts per 106 guanine (n=4). Although endogenous concentrations of 7-0EG in tissues in weanling rats were similar to those of adult rats, exogenous [13C2]-7-0EG concentrations were higher in weanlings, averaging 300 adducts per 106 guanine in liver. Studies on the persistence of [13C2]-7-0EG in adult rats sacrificed 2, 4, and 8 wks post exposure to [13C2]-VC demonstrated a half-life of 7-0EG of 4 days in both liver and lung.
