慢性低氧胁迫下虹鳟和硬头鳟生长、生化指标和基因表达的比较研究

COMPARATIVE STUDY ON GROWTH, BIOCHEMICAL INDEX, AND GENE EXPRESSION OF RAINBOW TROUT AND STEELHEAD UNDER CHRONIC HYPOXIA

  • 摘要: 为比较低氧胁迫对虹鳟、硬头鳟生长、血清生化指标、肝脏抗氧化酶活性和基因表达的影响, 研究设置4个处理组: 虹鳟常氧组(R-CT)、虹鳟低氧组(R-HY)、硬头鳟常氧组(S-CT)和硬头鳟低氧组(S-HY), 养殖周期为30d。结果显示: 低氧胁迫显著降低了虹鳟和硬头鳟的增重率、摄食量、特定增长率和热生长系数, 且两种鱼间不存在显著差异。在低氧环境下, 虹鳟血糖(GLU)水平减少、血清乳酸脱氢酶(LDH)水平增加; 而硬头鳟GLU水平增加、血清LDH水平减少, 表明低氧胁迫激活虹鳟肝脏糖酵解以应对自身能量供应短缺, 而硬头鳟糖酵解被抑制。低氧胁迫分别显著降低了虹鳟血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、碱性磷酸酶(ALP)和硬头鳟血清ALP水平, 表明虹鳟和硬头鳟代谢反应受到显著影响。低氧胁迫分别激活虹鳟肝脏过氧化氢酶(CAT)和硬头鳟肝脏超氧化物歧化酶(SOD)及CAT活性, 暗示硬头鳟活性氧(ROS)清除能力优于虹鳟。综合生物标志物响应(IBR)指数结果显示: R-HY组(6.61)>S-HY组(5.94)>S-CT组(0.43)>R-CT组(0.37), 表明低氧胁迫下虹鳟存活能力低于硬头鳟。低氧胁迫分别激活虹鳟肝脏血管生长因子(VEGF)和硬头鳟肝脏VEGF、葡萄糖转运蛋白1 (GLUT1) mRNA表达, 表明两者HIF-1信号通路低氧响应有所不同。综上, 在慢性低氧条件下(4.08±0.45) mg/L, 硬头鳟的耐低氧能力优于虹鳟, 且两种不同生活型鲑鳟鱼类的生理响应存在差异。

     

    Abstract: Under the combined pressures of global warming and water eutrophication, offshore salmonid aquaculture systems face increasingly threats from hypoxia during summer due to the expansion of oceanic anoxic zones. Landlocked rainbow trout (Oncorhynchus mykiss) and anadromous steelhead (Oncorhynchus mykiss) as the main culture species in deep-sea cage may exhibit different degrees of hypoxic tolerance caused by different life histories. To investigate the effects of chronic hypoxia on growth, serum biochemical, liver antioxidant enzyme activity, and related gene expression of rainbow trout and steelhead, we established four treatment groups as follows: rainbow trout normoxia group (R-CT), rainbow trout hypoxia group (R-HY), steelhead normoxia group (S-CT), and steelhead hypoxia group (S-HY). At the conclusion of 30d trial, our results demonstrated that chronic hypoxia significantly reduced the percent weight gain, total feed, specific growth rate, and thermal-unit growth coefficient in both rainbow trout and steelhead. However, there were no significant differences in growth observed between the two fish species. Following hypoxic stress, serum glucose (GLU) levels decreased while lactate dehydrogenase (LDH) activity increased in rainbow trout; whereas serum GLU levels increased and LDH activity decreased in steelhead. This suggests that liver glycolysis in rainbow trout was activated to meet energy demands under hypoxia, while it was inhibited in steelhead. Furthermore, levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) in rainbow trout serum, as well as serum ALP in steelhead, significantly decreased hypoxia, indicating substantial metabolic responses in both species. The activities of catalase (CAT) in rainbow trout liver, as well as superoxide dismutase (SOD) and CAT in steelhead liver, significantly increased under low-oxygen conditions, indicating superior ability to neutralize reactive oxygen species (ROS) in steelhead compared to rainbow trout. The integrated biomarker (IBR) index showed significant divergence among the different groups, with the R-HY group (6.61) > S-HY group (5.94) > S-CT (0.43) > R-CT groups (0.37), indicating inferior survival of rainbow trout compared to steelhead under hypoxia condition. The up-regulation of vascular endothelial growth factor (VEGF) in rainbow trout liver, as well as VEGF and glucose transporter 1 (GLUT1) in steelhead liver, in response to hypoxia suggests slightly different hypoxic responses in the HIF-1 signaling pathway of both fish species. In summary, this study demonstrated that rainbow trout are more sensitive to hypoxia (4.08±0.45) mg/L than steelhead, and significant physiological response were observed between the two salmonids life forms.

     

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