Aquaporin water channnels and osmoregulation in the European eel (Anguilla anguilla): the potential toxic effects of brominated flame retardants.

从简单的单细胞生物到复杂的多细胞动植物，包括哺乳动物和人类，水运输的调节对地球上所有形式的生命的生存都是至关重要的。水生生物在许多不同的淡水(FW)和海水(SW)生境中的进化成功和生存，也是由于复杂的相互关联的离子和水运输系统的发展，这些系统允许动植物在极端低渗和高渗环境中渗透调节和生存。这方面的研究很好的例子是泛盐生硬骨鱼，如欧洲鳗鱼，它们表现出遗传可塑性，能够在FW和SW环境中生存，而它们的体液渗透压和离子组成只有很小的变化。为了实现这一目标，真盐生硬骨鱼进化出了适应渗透调节策略的能力，允许从缺乏离子的FW栖息地排泄多余的水和清除盐分，同时在进入西南环境时逆转这些功能。这一过程的中心是称为水通道蛋白的膜转运蛋白大家族的关键功能，它不仅调节体内不同隔室之间的水运输，而且对于维持体液总量和外部环境中水的可获得性之间的平衡也是必不可少的。除了水，这些蛋白质的一个子集还能够运输包括甘油和尿素在内的小极性溶质，以及二氧化碳和氨等某些气体，这扩大了它们在所有生物体中的生理作用。所有水生生物，包括泛盐鳗，都依赖这些蛋白质的正常功能在FW和SW环境中生存，但这些蛋白质的不同作用，以及它们是如何被激素调节的，人们知之甚少。这项研究计划将确定鳗鱼渗透调节和生殖组织中存在水通道蛋白家族的哪些成员，并将描述其丰度和功能随着鱼类在FW和西南环境之间移动而发生的变化。这些研究将强调，当鳗鱼暴露在环境盐度的变化中时，水通道蛋白在维持体液成分方面发挥了关键的生理作用，环境盐度的变化通常与它们迁徙回马尾藻海繁殖有关。这项研究还将强调性成熟鳗鱼性腺发育中水通道功能的变化，最近在哺乳动物中报道，精子和卵子内水运输的变化是正常生殖发育的必要先决条件。在过去的30年里，鳗鱼数量在全球范围内急剧下降，据报道，一些地区的鳗鱼数量下降到了60年代末和70年代初S记录的不到10%。这一时期的数量下降与各种环境沉积物和废水中一组化学物质的增加和出现呈负相关关系，这些化学物质统称为溴化阻燃剂(BFR)。这些化学物质在环境中寿命极长，已知在各种食物链中的不同物种体内积累，一直到人类，包括人类。最近的报道表明，一些相对较低水平的BFR可以作为激素模拟物或拮抗剂发挥内分泌干扰作用，损害甲状腺激素和性类固醇的正常功能。作为该项目的一部分，我们将研究BFR对欧洲鳗鱼水通道蛋白功能的激素调节的潜在影响，因为这些毒素对这些水转运蛋白的有害影响可能会危及鱼类从FW环境到西南环境的成功迁徙和/或降低返回马尾藻的鱼类的繁殖力S

The regulation of water transport is fundamental to the survival of all forms of life on the planet, from simple uni-cellular organisms to complex multi-cellular plants and animals, including mammals and man. The evolutionary success and survival of aquatic organisms in many diverse freshwater (FW) and sea water (SW) habitats has also been made possible by the development of complex inter-related ion and water transport systems which allow animals and plants to osmoregulate and survive in extreme hypotonic and hypertonic environments. Well-studied examples of this are the euryhaline teleosts, such as the European eel, which exhibit the genetic plasticity to enable survival in both FW and SW environments with only minimal changes in the osmolality and ionic composition of their body fluids. In order to accomplish this, euryhaline teleosts have evolved the capacity to adapt their osmoregulatory strategies to allow the excretion of excess water and the scavenging of salts from ion-poor FW habitats while reversing these functions when entering SW environments. Central to this process is the critical function of members of a large family of membrane transporting proteins called aquaporins, that not only regulate water transport between various compartments within the body but are also essential to the maintenance of the equilibrium between total body fluid volume and water availability in the external environment. In addition to water, a subset of these proteins are also able to transport small polar solutes including glycerol and urea as well as certain gases such as carbon dioxide and ammonia, which extends their physiological roles within all organisms. All aquatic organisms, including the euryhaline eel, depend on the normal functioning of these proteins for survival in both FW and SW environments but the varied roles of these proteins, and how they are hormonally regulated are poorly understood. This research programme will determine what members of the aquaporin family are present in the osmoregulatory and reproductive tissues of the eel and will characterise changes in their abundance and function as fish move between FW and SW environments. These investigations will highlight the critical physiological roles played by the aquaporins in the maintenance of body fluid composition when eels are exposed to the changes in environmental salinity normally associated with their migration back to the Sargasso sea to breed. The study will also highlight changes in aquaporin function within the developing gonads of the sexually maturing eels, where it has recently been reported in mammals that changes in water transport within the sperm and egg are essential pre-requisites for normal reproductive development. Over the last 30 years there has been a dramatic world-wide decline in eel populations, with reports of populations in some areas dropping to less than 10% of that recorded in the late 60s and early 70's. This period of population decline exhibits an inverse relationship to the increasing production and appearance within various environmental sediments and effluents, of a group of chemicals collectively known as brominated flame retardants (BFRs). These chemicals are extremely long-lived in the environment and are know to be accumulating within different species in various food chains, all the way up to and including man. Recent reports indicate that relatively low levels of some BFRs can act as endocrine disruptors by functioning as hormone mimetics or antagonists, compromising the normal functions of the thyroid hormones and sex steroids. As part of this project we will investigate the potential effects of BFRs on the hormonal regulation of aquaporin function in the European eel as it is possible that deleterious effects of these toxins on these water transporters may compromise the successful migration of fish from FW to SW environments and/or reduce the reproductive fecundity of fish returning to the Sargasso s