Du Sherry N N, Mahalingam Sajeni, Borowiec Brittney G, Scott Graham R
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
J Exp Biol. 2016 Apr 15;219(Pt 8):1130-8. doi: 10.1242/jeb.132860. Epub 2016 Feb 19.
Many fish encounter hypoxia in their native environment, but the role of mitochondrial physiology in hypoxia acclimation and hypoxia tolerance is poorly understood. We investigated the effects of hypoxia acclimation on mitochondrial respiration, O2kinetics, emission of reactive oxygen species (ROS), and antioxidant capacity in the estuarine killifish ( ITALIC! Fundulus heteroclitus). Killifish were acclimated to normoxia, constant hypoxia (5 kPa O2) or intermittent diel cycles of nocturnal hypoxia (12 h:12 h normoxia:hypoxia) for 28-33 days and mitochondria were isolated from liver. Neither pattern of hypoxia acclimation affected the respiratory capacities for oxidative phosphorylation or electron transport, leak respiration, coupling control or phosphorylation efficiency. Hypoxia acclimation also had no effect on mitochondrial O2kinetics, but ITALIC! P50(the O2tension at which hypoxia inhibits respiration by 50%) was lower in the leak state than during maximal respiration, and killifish mitochondria endured anoxia-reoxygenation without any impact on mitochondrial respiration. However, both patterns of hypoxia acclimation reduced the rate of ROS emission from mitochondria when compared at a common O2tension. Hypoxia acclimation also increased the levels of protein carbonyls and the activities of superoxide dismutase and catalase in liver tissue (the latter only occurred in constant hypoxia). Our results suggest that hypoxia acclimation is associated with changes in mitochondrial physiology that decrease ROS production and may help improve hypoxia tolerance.
许多鱼类在其原生环境中会遭遇缺氧情况，但线粒体生理学在缺氧适应和缺氧耐受性中的作用却鲜为人知。我们研究了缺氧适应对河口鳉鱼（Fundulus heteroclitus）线粒体呼吸、氧气动力学、活性氧（ROS）释放以及抗氧化能力的影响。将鳉鱼分别置于常氧、持续缺氧（5 kPa O₂）或夜间间歇性缺氧（12小时常氧：12小时缺氧）的环境中适应28 - 33天，然后从肝脏中分离出线粒体。两种缺氧适应模式均未影响氧化磷酸化或电子传递的呼吸能力、漏呼吸、偶联控制或磷酸化效率。缺氧适应对线粒体氧气动力学也没有影响，但是在漏呼吸状态下的P50（使缺氧抑制呼吸达50%时的氧气张力）低于最大呼吸时的P50，并且鳉鱼线粒体在经历缺氧 - 复氧过程后，线粒体呼吸未受任何影响。然而，在相同氧气张力下比较时，两种缺氧适应模式均降低了线粒体ROS的释放速率。缺氧适应还增加了肝脏组织中蛋白质羰基的水平以及超氧化物歧化酶和过氧化氢酶的活性（后者仅在持续缺氧时出现）。我们的研究结果表明，缺氧适应与线粒体生理学变化相关，这些变化可减少ROS生成，并可能有助于提高缺氧耐受性。
