An oxidative DNA biomarker, 8-hydroxy-2'-deoxyguanosine (8-OHdG), was determined in the livers and kidneys of stranded or by-caught cetaceans along the Taiwan coast through isotope-dilution liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) to evaluate the feasibility of analyzing the DNA adduct in marine mammals and then to study the association between 8-OHdG and levels of polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) in the blubbers of the cetaceans. The mean values of the 8-OHdG from the liver and kidney samples were 19.83 +/- 10.00 pmol/mu mol deoxyguanosine (dG) (6.90-53.53 pmol/mu mol dG) and 19.16 +/- 7.48 pmol/mu mol dG (5.36-39.36 pmol/mu mol dG), respectively. In general, 8-OHdG was not related to the general health status of the by-caught and stranded animals and also was not related to species. However, the levels of 8-OHdG had a positive correlation with concentrations of PCBs, but not DDE, in female cetacean livers. In addition, when selected coplanar PCBs (dioxin-like congeners) were used to compare the 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) with 8-OHdG of by-caught cetaceans, a high positive correlation (r = 0.80, p < 0.01) was found in mature female animals. Thus, the detection of 8-OHdG in marine mammals with isotope-dilution LC/MS/MS is possible, and the study of the relationship between oxidative DNA damage and environmental contaminants under natural exposure indicates that the level of 8-OHdG in female cetacean livers is associated with coplanar PCBs and the factor of sexual maturity.
