Collaborative Research: The Evolution of Endocrine Function; Discovering the Hormonal Control of Osmoregulation in Basal Vertebrates

所有有生命的有机体都必须调节它们体内的盐分和水分含量，才能正常发挥作用并存活下来。在更复杂的动物中，如脊椎动物，激素及其结合的受体是参与调节盐和水运输的关键信号分子。鱼类与水直接接触，它们必须主动从淡水中吸收盐分，并在海水中积极分泌，才能调节体内的盐分浓度。到目前为止，关于盐分调节的激素控制的研究仅限于对高级鱼类的研究。这个项目将研究两种基本脊椎动物--鳗鱼和鲟鱼--盐分调节的激素控制。研究人员将研究生长激素和催乳素这两种由脑下垂体分泌的激素及其受体如何受到外界盐度的影响。这项研究将确定这些激素对七鳃鳗和鲟鱼耐受外界盐度变化的能力的影响。这些研究的结果将对这些激素的功能进化产生深刻的见解，进而可以应用于提高鱼类的农业产量和管理入侵的七鳃鳗。研究结果将被迅速转移到比较内分泌学和生理学的教科书中，发表在同行评议的期刊上，并在科学会议上分享。该奖项支持的研究将调查渗透调节激素在水生脊椎动物中的功能进化。我们目前对水生脊椎动物渗透调节激素控制的了解几乎完全来自高级硬骨鱼(硬骨鱼)，还没有关于脑垂体激素如何控制基础脊椎动物渗透调节的信息。现已证实，催乳素(PRL)对大多数硬骨鱼在淡水(FW)中的生存至关重要，生长激素(GH)至少在某些谱系中促进海水(SW)的渗透调节。七鳃鳗作为基本脊椎动物，软骨鱼(包括鲟鱼)作为基本骨性鱼类，具有与硬骨鱼相同的渗透调节策略(即，无论外部盐度如何，都保持几乎恒定的血浆离子水平)，但目前没有关于PRL或GH在七鳃鳗或软骨骨的渗透调节中发挥作用的信息。有强有力的证据表明，七鳗鱼只有一种催乳素/生长激素(PRL/GH)家族成员，这使得它们对这些研究特别关键。我们的具体目标是：1)确定生长激素和生长激素受体对七鳃鳗对盐度变化的反应；2)确定生长激素对七鳃鳗的渗透调节作用；3)确定生长激素和催乳素在鲟鱼中的渗透调节作用。对于每个物种，我们将研究FW和SW之间相互转移的生理和内分泌反应的时间进程。我们将利用重组技术制备七鳃鳗生长激素，以建立相应的放射免疫和放射受体分析方法，并测定其在体内和体外的渗透调节作用。

All living organisms must regulate their internal salt and water content to function routinely and survive. In more complex animals, such as vertebrates, hormones and the receptors to which they bind are critical signaling molecules involved in regulation of salt and water transport. Fish are in direct contact with water, and they must actively take up salts from freshwater and actively secrete them in seawater to be able to regulate internal salt concentrations. To date research on the hormonal control of salt regulation has been limited to studies on advanced fish species. This project will examine the hormonal control of salt regulation in two basal vertebrates, lamprey eel and sturgeon. The researchers will examine how growth hormone and prolactin, two hormones secreted by the pituitary gland, and their receptors are altered by external salinity. This research will determine the effect of these hormones on the ability of lamprey and sturgeon to tolerate changes in external salinity. The results of these studies will yield insights about the functional evolution of these hormones, which in turn could be applied to enhancing agricultural production of fish and management of invasive lamprey. The results will be rapidly transferred to textbooks in comparative endocrinology and physiology, published in peer-reviewed journals, and shared at scientific meetings. Studies supported by this award will investigate the functional evolution of osmoregulatory hormones in aquatic vertebrates. Our current understanding of the hormonal control of osmoregulation in aquatic vertebrates comes almost entirely from advanced bony fish (teleosts), and there is no information on how pituitary hormones control osmoregulation in basal vertebrates. It is now well-established that prolactin (PRL) is critical for survival of most teleosts in freshwater (FW) and that growth hormone (GH), at least in some lineages, promotes osmoregulation in seawater (SW). Lamprey, as basal vertebrates, and chondrosteans (including sturgeon), as basal bony fish, have the same osmoregulatory strategy as teleosts (namely, maintaining nearly constant levels of plasma ions irrespective of external salinity), yet there is currently no information on whether PRL or GH play a role in osmoregulation of either lamprey or chondrosteans. There is strong evidence that lamprey possess only one member of the PRL/GH family of pituitary hormones (GH), making them especially critical for these studies. Our specific aims are: 1) to determine the response of GH and GH receptor to salinity change in lamprey; 2) to determine the osmoregulatory actions of GH in lamprey; and 3) to determine the osmoregulatory roles of GH and PRL in sturgeon. For each species we will examine the time course of physiological and endocrine responses to reciprocal transfers between FW and SW. We will utilize recombinant technology to make lamprey GH in order to develop homologous radioimmuno- and radioreceptor- assays, and determine its osmoregulatory actions in vivo and in vitro.