Effects of increasing temperature on antioxidant defense system and oxidative stress parameters in the Antarctic fish Notothenia coriiceps and Notothenia rossii

Antioxidant defense system (ADS) and oxidative stress parameters were evaluated in the Antarctic fish Notothenia rossii and N. coriiceps exposed to increasing temperature. Acclimated fish were kept at 0 °C or exposed to 4 °C for 1 day (N. rossii) or to 2 and 4 °C for 1 and 6 days (N. coriiceps). Measurements were assessed in brain, gills, liver, white muscle and erythrocytes. Parameters analyzed included antioxidant capacity against peroxyl radicals (ACAP); reduced glutathione (GSH) and metallothionein-like proteins (MTLP) concentration; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutamate-cysteine ligase (GCL) activity; lipid peroxidation (LPO) level and protein carbonyl (PC) concentration. Increased liver GST activity was observed in N. rossii exposed to 4 °C for 1 day. Increased muscle GPx activity was observed in N. coriiceps after exposure to 2 °C for 1 day. Reduced gill GPx activity and increased liver SOD activity were observed after exposure to 4 °C for 1 day. In N. coriiceps, increased gill GCL activity and reduced gill GPx activity, as well as reduced liver MTLP were observed after exposure to 2 °C for 6 days. Reduced brain SOD activity and increased brain LPO; reduced gill ACAP, GSH concentration and GPx activity, as well as increased gill GCL activity; reduced liver ACAP, MTLP, SOD activity, GST activity and increased liver and erythrocytes LPO were observed after exposure to 4 °C for 6 days. These findings indicate that ADS is more responsive to short-term increasing temperature in the sluggish N. coriiceps than in the active N. rossii. However, responses of N. coriiceps to long-term increasing temperature were transient and did not prevent tissue oxidative damage. Considering the predicted increase in temperature in the Southern Ocean over the next decades, our findings suggest that Antarctic fishes are sensitive to ocean warming, displaying tissue oxidative damage associated with the thermal stress.