Effects of exposure to halogenated organic compounds combined with dietary restrictions on the antioxidant defense system in herring gull chicks.

The Herring gull (HG) (Larus argentatus) is naturally exposed to halogenated organic compounds such as polychlorinated biphenyls (PCBs) through its diet. During periods of food scarcity, arctic seabirds experience lipid mobilization, allowing stored lipid soluble contaminants to re-enter the body circulation. In the present study, we investigated the effects of PCB exposure and fasting on the antioxidant defense system in HG chicks. Forty newly hatched chicks were exposed to contaminated cod liver oil for 6weeks and then fasted for 1week. We assessed the hepatic total oxyradical scavenging capacity (TOSC) against peroxynitrite, hydroxyl and peroxyl radicals, and measured glutathione (reduced: GSH, and oxidized: GSSG) levels and the enzymatic activities of catalase, glutathione peroxidase, glutathione reductase and superoxide dismutase. The results show that fasting significantly increased the HOC levels in the HG chick livers. Limited effects were observed on antioxidant responses; significant effects were only found for catalase (CAT) activity, Se-dependent GPX activity and the GSH/GSSG ratio in the exposed and fasted group. CAT and Se-dependent GPX activities correlated negatively with the PCB concentrations within this group, and a nonlinear relationship between glutathione and contaminant levels was also found. These effects were generally not observed after exposure or fasting alone and were likely related to the high PCB levels induced by the combination of exposure and fasting.