Biochemical markers of dioxin-like toxicity and oxidative stress in hepatic microsomes of dream (Abramis brama) and perch (Perca fluviatilis) in the Elbe River

Biochemical markers of dioxin-like toxicity and oxidative stress were inves tigated in hepatic microsomal fractions of bream (Abramis brama) and perch (Perca fluviatilis) collected at six sites of the Elbe river (Czech Republi c). Concentrations of polychlorinated biphenyls (PCBs) and organochlorine p esticides were determined in pooled muscle samples to screen contamination rates of the sampling sites. Induction of the cytochrome P4501A-dependent 7 -ethoxy-resorufin O-deethylase (EROD) activity was used as the biomarker of dioxin-like toxicity, and the activation of microsomal glutathione 5-trans ferase (mGST) and in vitro susceptibility to lipid peroxidation were chosen as the biochemical markers of oxidative stress in fish. The concentrations of PCBs and DDT metabolites were higher in bream than perch tissues; the E ROD activity was higher in perch which were also found to be more susceptib le to oxidative damage to cellular membranes measured as Fe/NADPH-enhanced in vitro lipid peroxidation. Exposure to dioxin-like contaminants was detec ted at several sampling sites at which higher concentrations of PCBs and he xachlorobenzene were determined analytically. Both the oxidative stress par ameters were increased significantly at two sampling sites. At one of them, however, the results of chemical analyses indicate that the increases in l ipid peroxidation and mGST activity were caused by chemicals other than the contaminants monitored within this study. The parameters of oxidative stre ss can be regarded as important biomarkers of toxicity suited to complete r outine chemical analyses and screen the total chemical impact.