Response of antioxidant enzymes in freshwater fish populations (Leuciscus alburnoides complex) to inorganic pollutants exposure

Evidence is accumulating indicating the importance of antioxidant enzyme activity measurements in eco-toxicological studies, as they may constitute markers for exposure to a large variety of pollutants. Variation of antioxidant enzymes, superoxide dismutase (SOD) and glutathione S-transferases (GST) and the effect of heavy metals and selenium exposure on these enzymes were investigated in the livers of Iberian endemic minnows (Leuciscus alburnoides complex) captured in a copper (Cu) mining area. Higher hepatic levels of copper and selenium were always observed in fish captured at the polluted site relative to the reference area population, reflecting the environmental monitoring results. A seasonal fluctuation in zinc and selenium levels for both populations was also observed which could be related to gonad maturation. The activity of SOD did not show significant regional alterations, but a seasonal variation occurred presumably associated with the Leuciscus life cycle. The GST activity was higher in the fish population from the polluted area (except in spring) and GST variability was associated with selenium and copper levels when both regions were compared. The increased GST activity was probably a metabolic adaptation to the continuous exposure to higher levels of those elements.