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 seabream (Sparus aurata) by HPLC-EC. Susceptibility of different tissues to oxidative DNA damage was studied by exposing fish to model pollutants. Cu(II), paraquat (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 glucose-6-P dehydrogenase (G-6PDH) and GSSG reductase activities. The increased antioxidant status and the lack of a specific transport system could explain 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 fish 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 O2-rich organ and the lack of a significant increase in antioxidant defenses would explain the sensitivity of gills to DNA damage promoted by PQ. Elimination of this soluble chemical and the putative induction of DNA-repair enzymes specific for oxidative damages could explain the drop of 8-oxodG levels at longer times. Fish exposed to moderate levels of urban and industrial pollution showed significantly high 8-oxodG content in hepatic DNA. We conclude that 8-oxodG determination in chromosomal DNA by HPLC-EC is a potentially useful biomarker of environmental pollution, although its response is still somewhat lower than that of other well-established biomarkers of oxidative stress.

Mutagenic activation of aromatic amines by molluscs as a biomarker of marine pollution.

Mutagenic activation of arylamines by mollusc S9 fractions was evaluated as a biomarker for marine pollution. Two bivalve species were used as bioindicators, the common mussel (Mytilus edulis) and the striped venus (Chameleo gallina). A strain of Salmonella typhimurium overproducing O-acetyltransferase was used as indicator of mutagenicity. Mussels from an area of the North Atlantic Spanish zone that was exposed to an accidental crude oil spill were compared to bivalves from a reference area. C. gallina samples were from low polluted and highly polluted areas of the South Atlantic Spanish littoral. The promutagen 2-aminoanthracene (2-AA) was activated to mutagenic derivative(s) by S9 fractions from both C. gallina and M. edulis. Animals from contaminated sites showed higher arylamine activation capabilities than reference animals. This was further correlated with the mutagenic activities of corresponding cyclopentone-dichloromethane animal extracts. 2-AA activation by mollusc S9 was potentiated by alpha-naphthoflavone (ANF), known to inhibit PAH-inducible CYP1A cytochromes from vertebrates, but inhibited by methimazole (MZ), a substrate of the flavin monooxygenase (FMO) system. 2-AA-activating enzymes were mainly cytosolic; this localization clearly suggests that such activity could be attributed to soluble enzymes, different from the CYP1A or FMO systems. In conclusion, mutagenic activation of arylamines by mollusc S9, using as indicator a strain of Salmonella typhimurium that overproduces O-acetyltransferase, could be a reliable biomarker for marine pollution.

Metabolic activation of carcinogenic aromatic amines by fish exposed to environmental pollutants.

Activation of arylamines to mutagenic metabolites by hepatic S9 fractions has been evaluated as a biomaker of fish exposure to pollutants, using gilthead seabream (Sparus aurata), a valuable fish species from the Spanish South Atlantic littoral, as model organism. To obtain maximal sensitivity to the mutagenic action of aromatic amines, a strain of Salmonella typhimurium overproducing O-acetyltransferase was used. Fish were treated with Aroclor 1254, pesticides (malathion and dieldrin), or copper(II), and compared to Aroclor 1254-treated rats. The promutagen activation capabilities of the S9 fractions were further characterized by studying the effect of two monooxygenase inhibitors, alpha-naphthoflavone, a well known inhibitor of aromatic hydrocarbon-inducible forms of cytochrome P450, and methimazole, a substrate for the flavin monooxygenase (FMO) system. This study shows that 2-aminoanthracene (2-AA) and 2-acetylaminofluorene (AAF) activation by gilthead liver is enhanced by treatment of fish with different xenobiotics. The catalyst responsible for this enhanced activation appears to be different for each promutagen and, at least for 2-AA, dependent on the type of xenobiotic. The data presented indicate further that treatment of gilthead with some compounds, such as malathion and dieldrin, enhances the activation of aromatic amines in liver, without inducing ethoxyresorufin-O-deethylase activity. The use of acetyltransferase-overproducing bacteria appears to be a useful tool in the study of arylamine activation by fish liver, where biotransformation capability is lower than in mammals.