The antioxidant system of arctic seabirds and the effect of HOCs on antioxidant capacity of kidney tissue

Abstract

The arctic is exposed to a wide range of pollutants which originate from industrialized areas located in temperate regions. Halogenated organic contaminants (HOCs) are of special concern due to their persistency and ability to bioaccumulate. Consequently, animals high in the food chain, such as marine seabirds, are prone to accumulate high levels of these compounds. The HOCs are known to increase the formation of free radicals through metabolism and thereby jeopardise the balance between pro and antioxidant forces, which could lead to oxidative stress and therefore sever biological cell dysfunctions. The antioxidant system of kidney tissue of arctic seabirds has previously not been investigated as an organ for measuring effects of HOCs. In this study, single antioxidant parameters were measured in kidney tissue of three species of seabirds to investigate their species specific differences in antioxidant defences. The antioxidant parameters, catalase and glutathione peroxidase, glutathione reductase and total glutathione levels, revealed different species-specific antioxidant strategies in common eider, kittiwake and northern fulmar which are related to abiotic and biotic factors. In addition an experimental study was performed on herring gull chicks to assess the cause-effect relationship of exposure to HOCs, following parental transfer during feeding ,and fasting on the total oxidative scavenging capacity (TOSC) of their kidney tissue The TOSC assay provides an antioxidant scavenging profile, showing that exposure to HOCs significantly decrease the TOSC towards hydroxyl radicals and that exposure and fasting significantly increase the TOSC towards peroxynitrite and peroxyl radicals. We can conclude that parental transfer of HOCs to bird chicks can lead to biological effects in kidneys and effects are different between non fasting and fasting treatment. Finally, TOSC can be used as a biomarker on effects of HOCs in birds.