Oxidative stress in pied flycatcher (Ficedula hypoleuca) nestlings from metal contaminated environments in northern Sweden

Metals have been shown to induce oxidative stress in animals. One of the most metal polluted terrestrial environments in Sweden is the surroundings of a sulfide ore smelter plant located in the northern part of the country. Pied flycatcher nestlings (Ficedula hypoleuca) that grew up close to the industry had accumulated amounts of arsenic, cadmium, mercury, lead, iron and zinc in their liver tissue. The aim of this study was to investigate if pied flycatcher nestlings in the pollution gradient of the industry were affected by oxidative stress using antioxidant molecules and enzyme activities. The antioxidant assays were also evaluated in search for useful biomarkers in pied flycatchers. This study indicated that nestlings in metal contaminated areas showed signs of oxidative stress evidenced by up regulated hepatic antioxidant defense given as increased glutathione reductase (GR) and catalase (CAT) activities and slightly but not significantly elevated lipid peroxidation and glutathione-S-transferase (GST) activities. Stepwise linear regression indicated that lipid peroxidation and CAT activities were influenced mostly by iron, but iron and lead influenced the CAT activity to a higher degree. Positive relationships were found between GST and lead as well as GR activities and cadmium. We conclude that GR, CAT, GST activities and lipid peroxidation levels may function as useful biomarkers for oxidative stress in free-living pied flycatcher nestlings exposed to metal contaminated environments.