Oxidative stress, liver biotransformation and genotoxic effects induced by copper in Anguilla anguilla L. – the influence of pre-exposure to β-naphthoflavone

Fish are exposed in the aquatic ecosystems to different classes of pollutants. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals represent two important classes of aquatic contaminants. Thus, one lot of European eels (Anguilla anguilla L.) was pre-exposed during 24 h to 2.7 μM β-naphthoflavone (BNF; a PAH-like compound), and subsequently exposed during 24 h to 0, 1 and 2.5 μM copper (Cu). Additionally, another lot not pre-exposed to BNF was exposed to the same Cu concentrations. BNF pre-exposure promoted a significant increase in liver ethoxyresorufin O-deethylase (EROD) activity, but did not change the other responses investigated in eels. On the other hand, both Cu concentrations did not modify the liver EROD activity either in eels pre-exposed to BNF or not. Liver total cytochrome P450 was increased in eels exposed to Cu 2.5 μM, being significantly only in eels not pre-exposed to BNF. Free sulfhydryl group content was decreased by 1 and 2.5 μM in eels pre-exposed to BNF or not pre-exposed, being significant at 2.5 μM Cu in eels not pre-exposed compared to its control. Liver total glutathione (TG), reduced glutathione (GSH) and GSH/oxidized glutathione (GSSG) levels were slightly decreased by 1 and 2.5 μM Cu in eels pre-exposed to BNF, whereas a slight tendency to increase was observed in eels not pre-exposed. Thus, liver TG and GSH significantly decreased in 2.5 μM Cu BNF pre-exposed eels compared to eels not pre-exposed to BNF. Liver glutathione reductase and catalase activities were significantly inhibited by 1 and 2.5 μM Cu in eels pre-exposed to BNF, concomitantly with a slight liver glutathione peroxidase tendency to decrease. Lipid peroxidation was significantly increased by 1 μM Cu in eels either pre-exposed or not pre-exposed to BNF. Liver H2O2 was significantly increased by 1 μM Cu in eels pre-exposed to BNF. Liver DNA integrity was significantly decreased by 1 and 2.5 μM Cu in eels pre-exposed to BNF. The oxidative stress and genotoxic effects induced by Cu in eels pre-exposed to BNF revealed that the metal effects are potentiated by previous exposure to BNF.