Temperature and hypoxia on oxidative stress responses in pacu Piaractus mesopotamicus.

The aim of this study was to verify the effects of the interaction between different temperatures and levels of dissolved oxygen in the oxidative stress parameters of pacu juveniles. A total of 81 pacu juveniles (61.7 ± 9.1 g) were exposed to three temperatures (18, 23, and 28 °C), acclimated for a period of 30 days, and then submitted to three levels of dissolved oxygen: control or normoxia (7 mg L-1); moderate hypoxia (4 mg L-1); and severe hypoxia (2 mg L-1) for 12 h. Glutathione-S-transferase (GST) activity, total antioxidant capacity against peroxyl radicals (ACAP), and protein thiol content (PSH) and LPO (lipid peroxidation) [measured by the TBARS] were measured in gill, liver, muscle and brain. The results indicated that the interaction between different temperatures and dissolved oxygen levels caused alterations in the antioxidant system and induced lipid and protein damage in pacu juveniles. In addition, the effects were organ specific. In conclusion, exposure to moderate and severe hypoxia affect oxidative stress parameters and have been shown to be organ-specific in pacu juveniles. The interaction between 23 °C and hypoxia caused greater disturbances in oxidative stress markers, such as PSH in the gills and liver and LPO in the muscle.

Oxidative stress and antioxidant responses in juvenile Brazilian flounder Paralichthys orbignyanus exposed to sublethal levels of nitrite.

This study evaluated the effects of short-term exposure to sublethal levels of nitrite on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus. An assessment of fish recovery was also performed. Fish were exposed to 0.08 (control), 5.72, 10.43, and 15.27 NO2-N mg L-1 for 10 days followed by the same recovery time. Gill, liver, and muscle samples were collected after 1, 5, and 10 days of exposure and after recovery for the measurement of antioxidant capacity against peroxyl radicals (ACAP), glutathione-S-transferase (GST) activity, content of non-protein (NPSH) and protein thiols (PSH), and lipid peroxidation levels by thiobarbituric acid-reactive substances (TBARS) content. Nitrite exposure induced alterations which compromised the overall antioxidant system (reduced ACAP and GST activity) and enhanced oxidative damage in lipids and proteins. Increases in GST activity and NPSH and PSH contents were also demonstrated. The recovery period allowed for resumption of basal levels for all (treatment 5.72 NO2-N mg L-1) or some of the evaluated parameters (other treatments). In conclusion, exposure to nitrite concentrations from 5.72 to 15.27 NO2-N mg L-1 induced oxidative stress and antioxidant responses in juvenile Brazilian flounder. The 10-day recovery period was sufficient for a complete resumption of basal physiological condition of fish exposed to concentrations of up to 5.72 NO2-N mg L-1.