Effects of hypoxia on lysozyme activity and antioxidant defences in the kidney and spleen ofCarassius auratus

Abstract

Assessing the responses of lysozyme activity and antioxidant defences to hypoxia is important to understand the adaptation and tolerance strategies of fish under hypoxia. This study investigated the effects of different dissolved oxygen (DO) levels on Carassius auratus, a natural triploid fish, from Qihe River. The content of malondialdehyde (MDA) and the activities of lysozyme and antioxidant enzymes were measured in the kidney and spleen after hypoxic exposure. At the DO concentrations of 1 and 2 mg L À1 , the activities of antioxidant enzymes and lysozyme significantly decreased and the content of MDA significantly increased (P < 0.01). This result suggests that hypoxia decreased antioxidant enzyme and lysozyme activities and caused MDA accumulation in a concentration-dependent manner. The DO level of 4 mg L À1 increased the activities of superoxide dismutase and catalase in the kidney and the activities of glutathione peroxidase and catalase in the spleen (P < 0.05). This result implies that slight hypoxic stress can enhance antioxidant defences to alleviate the damage of oxidative stress. The reduced activities of antioxidant enzymes and the accumulation of MDA at the DO level of ≤2 mg L À1 implied the decrease in antioxidative ability and the occurrence of oxidative stress. The decrement in lysozyme activity indicated that the antibacterial ability was weakened to some degree. Therefore, hypoxic stress at DO levels ≤2 mg L À1 should be removed by aeration to avoid the oxidative damage resulting from the reduced antioxidative ability and prevent the outbreak of diseases caused by weakened antibacterial effects.

The effects of dissolved oxygen and dietary protein levels on growth performance, physiological parameters and the immune response of the genetically improved farmed tilapia juveniles (Oreochromis niloticus)

“…The rise in the liver MDA content of GIFT juveniles could signal a massive production of lipid peroxidation (LPO) (Hegazi et al., 2010) resulting from the hypoxia‐induced oxidative stress. Similar results were reported on Carassius auratus (Zhao et al., 2017) and sea cucumber Apostichopus japonicas (Huo et al., 2018). Avellini et al.…”

Impact of hypoxia stress on the physiological responses of sea cucumber Apostichopus japonicus: respiration, digestion, immunity and oxidative damage

“…Previous studies have shown that MDA accumulation is positively related to the level of oxidative stress ( Shi et al, 2005 ; Sun et al, 2008 ). Moreover, significantly increased content of MDA was observed in Carassius auratus under hypoxia ( Zhao et al, 2017 ). In the present study, the content of MDA in coelomic fluid from sea cucumber increased about twofold under hypoxia, suggesting that hypoxia stress caused lipid peroxidation resulting from oxidative stress.…”

Molecular characterization of mudskipper (Boleophthalmus pectinirostris) hypoxia-inducible factor-1α (HIF-1α) and analysis of its function in monocytes/macrophages

“…Aquatic hypoxia induces changes in the fish immune system, involving cytokines, granulocytes, and macrophages [ 4 – 6 ]. Slight hypoxic stress can elevate non-specific immune responses in fish, but severe hypoxic challenge results in immunosuppression [ 7 , 8 ]. Therefore, hypoxia is now considered as a potential regulator of immunity.…”