Journal
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY
Volume 224, Issue -, Pages 53-67Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.cbpa.2018.05.019
Keywords
Hypoxia tolerance; Loss of equilibrium; Oxidative damage; Oxidative stress; Pcrit
Categories
Funding
- Brazilian government through FAPEAM
- CNPq [315908, 0621187, 573976/2008-2, 465540/2014-7]
- Ciencia sem Fronteiras grant [400311/2012-7]
- CMW through a Natural Sciences and Engineering Research Council of Canada (NSERC) [RGPIN 4732012]
- Canada Research Chairs program [2007M00011]
- Brazilian government through CNPq [303930/2014-4, 304758/2015-9]
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We examined whether oxidative damage and antioxidant responses are more likely to occur during hypoxia or re-oxygenation in hypoxia-tolerant fish, and whether there is an influence of the rate of re-oxygenation. An hypoxia/re-oxygenation experiment using wild-caught Cyphocharax abramoides (Rio Negro, Brazil), was designed to answer these questions. Lipid peroxidation (MDA), a measure of oxidative damage, and antioxidant activities (superoxide dismutase (SOD), glutathione peroxidase (GPx), antioxidant capacity against peroxyl radicals (ACAP)), were measured in brain, gill and liver tissues after normoxia, 3-h hypoxia (2.7 kPa), and 3-h hypoxia followed by 1-h or 3-h re-oxygenation, implemented either immediately or slowly (3.0 kP.h(-1)). Critical oxygen tension of routine oxygen consumption rate (Pcrit) (4.1 kPa) and the P-O2 at loss of equilibrium (LOE) (1.7 kPa) were determined to set the experimental hypoxia exposure. The Regulation Index, a measure of oxyregulation with declining P-O2, was 0.32. Oxidative damage occurred during hypoxia: no additional damage was observed during re-oxygenation. Tissues responded differentially. GPx and MDA rose in the brain and gills, and SOD (and likely GPx) in the liver during hypoxia. Antioxidants increased further at LOE. Rate of oxygen increase during re-oxygenation did not affect antioxidant responses. In brain and gills, GPx and MDA decreased or recovered after 1-h re-oxygenation. In liver, SOD remained high and GPx increased. In summary, C. abramoides incurred oxidative damage during hypoxic exposure with no additional damage inflicted during re oxygenation: the rate of re-oxygenation was inconsequential. Literature data support conclusion of greater damage during hypoxia than during re-oxygenation in hypoxia-tolerant fish.
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