The regulation of urea excretion in a batrachoidid fish

海湾蟾鱼Opsanus beta是一种不同寻常的鱼，它以不同的脉冲排泄尿素作为其主要的氮废物产品，通过测量周围水中尿素的出现突然增加来衡量。从蟾鱼鳃中克隆出一种尿素转运蛋白，它的氨基酸序列与哺乳动物的尿素转运蛋白相似，尿素的脉冲被认为是由于TUT的周期性激活，允许尿素从血液中通过鳃进入水中。然而，图坦卡蒙是如何开启和关闭的还不是很清楚，但到目前为止的研究已经确定，压力荷尔蒙皮质醇和神经递质5-羟色胺(5-HT)参与了这一过程。高水平的皮质醇似乎阻止了TUT的激活，而5-羟色胺则刺激了TUT的功能。5-羟色胺的作用可能是由5-羟色胺受体亚型介导的，该亚型具有与哺乳动物5-羟色胺2A型(5-HT2A)受体相似的药理特征。本项目旨在通过研究皮质醇和5-羟色胺如何控制图坦卡蒙的功能，并确定皮质醇和5-羟色胺的作用是否相互影响，来进一步研究图坦卡蒙的调节。分子技术和体外组织制备将与整体动物研究并行使用，以检验图坦卡蒙的功能直接受5-羟色胺控制、皮质醇间接控制的假设。这些研究还将检验一种假设，即TOADFISH的5-HT2A受体参与了TUT的激活，而当皮质醇水平较高时，这些受体无法激活TUT。该项目的发现将扩大我们对鱼类和陆地生物体内氮素废物代谢和排泄的了解。此外，这项研究的结果将为深入了解5-羟色胺和皮质醇之间的相互作用提供线索，皮质醇是几种人类疾病的核心信号。迈阿密大学有一个多元化的学生群体，这个项目将为科学和工程领域代表性不足的学生提供研究经验。

The Gulf toadfish, Opsanus beta, is an unusual fish that excretes urea as its primary nitrogen waste product in distinct pulses, measured by a sudden increase in the appearance of urea in the surrounding water. A urea transporter has been cloned from toadfish gill (tUT) that is similar in amino acid sequence to mammalian urea transporters and the pulse of urea is believed to be due to the periodic activation of tUT, allowing for the movement of urea from the blood, across the gill, into the water. How tUT is turned on and off is not well understood, however, but research to this point has determined that the stress hormone, cortisol, and the neurotransmitter, serotonin (5-HT), are involved. High levels of cortisol appear to prevent tUT activation while 5-HT stimulates tUT function. The action of 5-HT appears to be mediated by a serotonin receptor subtype with pharmacological characteristics similar to mammalian serotonin type 2A (5-HT2A) receptors. This project aims to further examine the regulation of tUT by investigating how cortisol and 5-HT control tUT function and determine whether the actions of cortisol and 5-HT influence each other. Molecular techniques and in vitro tissue preparations will be used in parallel with whole animal studies to test the hypothesis that tUT function is controlled directly by 5-HT and indirectly by cortisol. These studies will also test the hypothesis that toadfish 5-HT2A receptors in the gill are involved in tUT activation and these receptors are not able to activate tUT when cortisol levels are high. The findings of this project will expand our understanding of nitrogen waste metabolism and excretion in fish and terrestrial organisms. In addition, results of this research will provide insight into the interactions between 5HT and cortisol, signals that are central to several human disorders. University of Miami has a diverse student body and this project will provide research experiences for students who are underrepresented in science and engineering.