Physiological, Biochemical Responses and Apoptosis- Related Genes Expressions of Hypoxia and Re- Oxygenation Stress in an Economically Important Mariculture Fish, the Chinese Sea Bass (Lateolabrax maculatus)
The Chinese sea bass (Lateolabrax maculatus) is one of the most important marine aquaculture fish in China. Hypoxia represents a growing threat to L. maculatus in intensive mariculture. Here, effects of hypoxia and re-oxygenation conditions on physiological, biochemical responses and apoptosis-related genes expressions in L. maculatus were investigated. The results showed that the asphyxiation point and critical non-equilibrium point of adult L. maculatus were 0.39 mg/L and 1.17 mg/L dissolved oxygen, respectively. The concentrations of four inorganic ions (Na+, K+, Cl-, Ca2+) in serum and four red blood cell parameters levels (HCT, MCV, MCHC, RDW-CV) were significantly changed in hypoxic and re-oxygenated fish. The concentration of hepatic glycogen was decreased dramatically in re-oxygenated fish compared with control and hypoxic fish, which is contrary to the result of glucose, total cholesterol and triglyceride in serum. Moreover, the activities of certain myocardial enzymes (LDH, CK, CK-MB) were significantly increased in the serum occurred in cardiomyocytes during re-oxygenated condition, speculating that hypoxia/re- oxygenation injury might be occurred in cardiomyocytes. The result of six apoptosis- related genes expressions in heart of L. maculatus showed that pro-apoptotic genes (Cytc, Caspase3, Bax, Stat3) were significantly up-regulated in re-oxygenated condition whereas anti-apoptotic genes were (TET1, SGK1) expressed lower in re-oxygenated condition than that in normal. The experimental results suggested that hypoxia and re-oxygenation had a serious impact on L. maculatus, such as ion balance destroying, innate immune decreasing, oxygen carrying capacity changing, cardiomyocyte apoptosis. Especially, cardiomyocyte injury caused by hypoxia and re-oxygenation after hypoxia is very severely. These findings might be helpful for breeding management and future hypoxia stress study in L. maculatus
