Oxidative stress parameters in juvenile Brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839) (Pleuronectiformes: Paralichthyidae) exposed to cold and heat shocks

The aim of this study was to determine oxidative stress parameters in the liver and gill of Brazilian flounder juveniles (307.0 +/- 16.0 g and 30.0 +/- 4.0 cm) submitted to different water temperature (17.1, 23.0 and 28.8 degrees C) for 72 h and maintained at salinity 25%. After the acclimation of 7 days, in 23 degrees C, fish were transferred to 200 L tanks containing seawater (salinity 25%) at 28.8 degrees C (heat shock), 17.1 degrees C (cold shock) or 23.0 degrees C (control), five replicates (five fish tank(-1)). The sampled collection occurred in 0 (pre-challenge), 3, 24, 48 and 72 h after temperature shock. Flounder exposed to 17.1 degrees C and 28.8 degrees C showed significantly higher TBARS levels and GST activity in the liver post-exposition (PE) in relation to the control (23 degrees C). CAT activity in liver present a significantly increase at 17.1 degrees C, in first 48 h, and subsequently decrease in 72 h PE in relation to 28.8 degrees C. The gills of flounder showed significantly higher TBARS levels, GST and CAT activity when submitted at 17.1 and 28.8 degrees C in relation to 23.0 degrees C. There were observed changes in lipid peroxidation levels (LPO), CAT and GST activities in the liver and gill of Brazilian flounder in response to reactive oxygen species (ROS) produced by thermal shocks.