The endocrine regulation of salt and water balance in aquatic organisms

我的研究项目是研究内分泌因素（如激素）如何使水生动物保持盐和水的平衡。在这个背景下，所有的淡水动物和许多海洋物种都生活在这样的环境中：盐的被动运动，要么进入我们的身体，要么离开我们的身体，如果没有专门负责盐运输的组织和器官的控制，将会造成危及生命的问题。例如，淡水（FW）的含盐量（如钠、氯和钙等离子）远低于动物血液中的含盐量，离子通过被动扩散从体内流失到周围环境中。相比之下，许多海水动物面临着相反的问题，因为在这些物种中，海水比血液更咸，离子会扩散到动物体内。此外，水生动物可能生活在环境含盐量发生自然变化的地方（如河口潮汐变化）或人为干扰（如道路加盐）正在改变水含盐量的地方。在所有这些情况下，激素对特殊离子运输组织的作用调节了组织的形式和功能，从而维持了盐和水的平衡。在水生动物中，这些特化组织包括鳃上皮、肾脏、胃肠道和皮肤。上皮组织建立屏障，分离和调节流体间生物材料的运动（例如鳃上皮分离血液和水并调节它们之间的离子运动）。从一个液体室到另一个液体室的上皮离子转运有两条途径。第一种是通过细胞（跨细胞途径），第二种是细胞之间（细胞旁途径）。跨细胞离子运输是由一套复杂的转运蛋白和离子通道控制的，这在水生动物中得到了很好的描述，激素对其功能的影响也是如此。细胞旁通路由脊椎动物的紧密连接（TJ）复合体或无脊椎动物的分隔连接（SJ）复合体的蛋白质控制。与跨细胞转运蛋白相比，我们对水生动物中的TJ和SJ蛋白知之甚少，而且几乎不知道内分泌因素如何（或什么）影响它们。这是令人担忧的，因为水生动物的细胞旁通路的渗透性被广泛认为在盐和水平衡的调节中起着至关重要的作用。因此，我们在水生动物如何在自然环境中发挥作用以及这些生物如何应对环境变化的基本知识方面存在严重差距。我的工作通过识别水生动物中重要的TJ和SJ蛋白，并使用现有的和最新的最先进的技术密切关注TJ和SJ通透性的内分泌调节，解决了这一知识的缺乏。在这方面，我们的研究对任何对水生生物如何维持“体内平衡”（即内部稳定性）感兴趣或对生物材料如何跨越水生动物上皮屏障感兴趣的人都很重要。这是一个广泛的人群，从那些有基础研究兴趣的人，到那些调查污染物的影响和人类活动对水生生物的影响的人，以及那些寻求通过细胞旁途径优化生物材料（例如药物）向水生生物的传递的人。

My research program examines how endocrine factors (e.g. hormones) allow aquatic animals to maintain salt and water balance. To put this in context, all freshwater (FW) animals and a great many marine species live under conditions where passive salt movement either into our out of the body will create life-threatening problems if not held in check by tissues and organs that specialize in salt transport. For example, the salt content (e.g. ions such as sodium, chloride and calcium) of freshwater (FW) is considerably lower than that of animal blood and ions are lost from the body to the surroundings by passive diffusion. In contrast, many seawater (SW) animals suffer the opposite problem because in these species SW is saltier than blood, and ions diffuse into the animal. Furthermore, aquatic animals may live where natural alterations in environmental salt content occur (e.g. changing tides in an estuary) or where human disturbance (e.g. road salting) is changing water salt content. In all these circumstances, the action of hormones on specialized ion transporting tissues adjusts the form and function of the tissues so as to allow the maintenance of salt and water balance. In aquatic animals, these specialized tissues include epithelia of the gill, kidney, gastrointestinal tract and skin. Epithelial tissues establish barriers that separate and regulate the movement of biological material between fluid compartments (e.g. the gill epithelium separates blood and water and regulates ion movement between them). Transepithelial ion transport, from one fluid compartment to another, occurs by two routes. The first is through cells (the transcellular pathway) and the second is between cells (the paracellular pathway). Transcellular ion transport is governed by a complex suite of transport proteins and ion channels that are well described in aquatic animals, as is the effect of hormones on their function. The paracellular route is governed by proteins of the tight junction (TJ) complex in vertebrates or septate junction (SJ) complex in invertebrates. In contrast to transcellular transport proteins, very little is known about TJ and SJ proteins in aquatic animals, and almost nothing is known about how (or what) endocrine factors influence them. This is alarming because the permeability of the paracellular pathway in aquatic animals is broadly acknowledged to play a vital role in the regulation of salt and water balance. As such we are presented with a serious gap in our fundamental knowledge of how aquatic animals function in their natural environment and how these organisms are equipped to cope with environmental change. My work addresses this lack of knowledge by identifying important TJ and SJ proteins in aquatic animals and looking closely at the endocrine regulation of TJ and SJ permeability using established and new state-of-the-art techniques. In this regard, our research is important to anyone who has an interest in how aquatic organisms maintain "homeostasis" (i.e. internal stability) or who are interested in how biological material moves across the epithelial barriers of aquatic animals. This is a broad populace that will range from those with basic research interests, to those who investigate the effects of pollutants and the impact of human activity on aquatic organisms, as well as those that seek to optimize the delivery of biological material (e.g. drugs) to aquatic organisms via the paracellular pathway.