Content of 8-oxodG in chromosomal DNA of Sparus aurata fish as biomarker of oxidative stress and environmental pollution

The 8-oxodG content has been measured in chromosomal DNA of gilthead seabre am (Sparus aurata) by HPLC-EC. Susceptibility of different tissues to oxida tive DNA damage was studied by exposing fish to model pollutants. Cu(II), p araquat (PQ) and malathion failed to promote DNA oxidation in liver, while dieldrin significantly increased the 8-oxodG content in this organ, but not in gills or blood. After PQ exposure, fish liver showed high levels of glu cose-6-P dehydrogenase (G-6PDH) and GSSG reductase activities. The increase d antioxidant status and the lack of a specific transport system could expl ain the lack of susceptibility of liver to DNA oxidative damage induced by PQ. Increased levels of 8-oxodG were detected in the gills of PQ-exposed fi sh after 8 and 24 h. In contrast, after 48 h exposed fish contained lower 8 -oxodG levels than controls. The existence of a PQ transport system in this O-2-rich organ and the lack of a significant increase in antioxidant defen ses would explain the sensitivity of gills to DNA damage promoted by PQ. El imination of this soluble chemical and the putative induction of DNA-repair enzymes specific for oxidative damages could explain the drop of 8-oxodG l evels at longer times. Fish exposed to moderate levels of urban and industr ial pollution showed significantly high 8-oxodG content in hepatic DNA. We conclude that 8-oxodG determination in chromosomal DNA by HPLC-EC is a pote ntially useful biomarker of environmental pollution, although its response is still somewhat lower than that of other well-established biomarkers of o xidative stress. (C) 1999 Elsevier Science B.V. All rights reserved.