Mechanisms of nitrogen excretion, toxicity and tolerance in ancient and modern fishes

古代和现代鱼类的氮排泄、毒性和耐受性机制

• 批准号: 194686-2010
• 负责人: Wilkie, Michael
• 金额: $ 1.97万
• 依托单位: Wilfrid Laurier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=523259
• 关键词: Mechanisms; nitrogen; excretion; toxicity; tolerance

The overarching aim of my research is to determine how fishes produce and excrete nitrogenous wastes (N-wastes) such as ammonia and urea, and how they cope with potentially toxic build-ups of these products. The breakdown of excess amino acids generates neurotoxic ammonia that must either be excreted or converted to less toxic wastes such as urea. Although ammonia targets the central nervous system (CNS), its precise mechanism of toxicity is unresolved. Blood and CNS ammonia may reach toxic concentrations due to liver failure in mammals. In fishes, internal ammonia increases following feeding, and when excretion by the gill is prevented by altered water chemistry (e.g. > water pH) or elevated water ammonia arising from natural (e.g. decomposition of organic material) or anthropogenic sources (e.g. sewage effluent, agricultural run-off). I propose to determine how N-waste excretion systems in fishes are influenced by feeding and life-stage, and to identify the underlying mechanisms of ammonia toxicity and tolerance. Sea lampreys will be the model for studying excretion. My previous work demonstrated that feeding profoundly stimulated ammonia and urea excretion in parasitic lampreys as they fed on the blood of sharks and trout, making them ideal for learning more about the mechanisms and evolution of N-waste excretion strategies in vertebrates. Goldfish and trout will be used to determine how the CNS of fishes copes with build-ups of ammonia when excretion is impaired or after feeding. My objectives for the next 5 years will be to: (i) determine how ammonia and urea transport systems are altered during the lamprey life-cycle and by feeding, (ii) identify the mechanisms of acute ammonia toxicity and tolerance in the CNS of goldfish and more ammonia-sensitive trout, and (iii) ascertain how feeding and prolonged sub-lethal ammonia exposure affect the ammonia-tolerance and CNS of goldfish and trout. The integrative approach I will use will include whole animal models, cultured brain cells, molecular techniques, and electrophysiology. This research will answer fundamental questions on the mechanisms and evolution of waste excretion in vertebrates, and it may identify novel mechanisms of ammonia tolerance in fish.

我研究的主要目的是确定鱼类如何产生和排泄氨和尿素等含氮废物，以及它们如何应对这些产品的潜在有毒堆积。过量氨基酸的分解会产生神经毒性的氨，必须将其排出或转化为毒性较低的废物，如尿素。虽然氨以中枢神经系统(CNS)为靶标，但其确切的毒性机制尚不清楚。由于哺乳动物的肝功能衰竭，血液和中枢神经系统的氨可能达到有毒浓度。在鱼类中，当摄食后体内的氨增加，并且当鳃的排泄被水化学变化(例如水的pH值)或自然(例如有机物的分解)或人为来源(例如污水排放、农业径流)引起的升高的水氨所阻止时。我建议确定鱼类的氮废物排泄系统如何受摄食和生活阶段的影响，并确定氨毒性和耐受性的潜在机制。七鳃鳗将成为研究排泄物的模型。我以前的工作证明，当寄生七鳃鳗以鲨鱼和鲑鱼的血液为食时，摄食可以极大地刺激它们的氨和尿素排泄，使它们成为更多了解脊椎动物N废物排泄策略的机制和进化的理想选择。金鱼和鲑鱼将被用来确定当排泄受损或进食后，鱼类的中枢神经系统如何应对氨的积聚。我未来5年的目标将是：(I)确定氨和尿素运输系统在七鳃鳗生命周期和摄食过程中是如何改变的，(Ii)确定金鱼和对氨更敏感的鲑鱼中枢神经系统中急性氨毒性和耐受性的机制，以及(Iii)确定摄食和长期亚致死性氨暴露如何影响金鱼和鲑鱼的耐氨性和中枢神经系统。我将使用的综合方法将包括完整的动物模型、培养的脑细胞、分子技术和电生理学。这项研究将回答脊椎动物排泄废物的机制和进化的基本问题，并可能识别鱼类耐氨性的新机制。