Oxidative stress in juvenile tambaqui (Colossoma macropomum) after different periods of air exposure

Abstract

This study evaluated the response of juvenile Colossoma macropomum to oxidative stress when exposed to air for different periods of time. Fifty-four juveniles weighing 74.8 ± 17.4 g were randomly transferred to nine 30-L tanks in a recirculating aquaculture system and acclimatized to experimental conditions for 15 days. The fish were subsequently fasted for 24 h, after which a group of animals (n = 6) was sampled immediately at the beginning of the experiment to determine baseline levels (without air exposure). Another group (n = 24) was exposed to air for 30 min (30E) and the rest of the fish (n = 24) were exposed to air for 60 min (60E). Oxidative damage and antioxidant defenses were determined immediately after air exposure (IAE; n = 6) and at 1, 24 and 48 h after air exposure (1hAE, 24hAE, and 48hAE; n = 6 animals/per exposure time) by euthanizing fish and immediately removing the gills, liver, kidney, and brain. The interaction between factors (air exposure time x collection time) had an effect on reduced glutathione in the liver (P < 0.0001) and kidney (P = 0.0252). The highest concentrations for reduced glutathione in the gills was for treatment 60E (P = 0.0294), while that for the brain was for treatment 30E (P = 0.0012). Air exposure time had an effect on liver (P < 0.0001) and kidney (P < 0.0001) superoxide dismutase, with the highest values for 60E and 30E, respectively. The interaction between factors had an effect on liver protein levels (P = 0.0029), with the highest value for 30E at 24hAE. Treatment 60E had higher protein degradation in the gills, kidneys and brain than treatment 30E (P < 0.05). Treatment 30E had lower TBARS concentrations in the liver (P = 0.0284) and gills (P = 0.0012), but without damage to the kidney (P = 0.9396) and brain (P = 0.5277). Therefore, air exposure caused changes in antioxidant defenses in the liver, kidney, brain, and gills of C. macropomum juveniles.