Intestinal Bicarbonate Secretion, Osmoregulation and Acid-Base Balance in Marine Fish

含盐的海洋环境正在脱水，海水是海水唯一的水合来源。在陆生动物中，摄入海水会导致严重的腹泻，而腹泻本身就是脱水。相比之下，海鱼能够从摄入的海水中吸收液体，并能够成功地消除相关的盐分增加。本项目旨在进一步描述允许这些脊椎动物在海洋环境中大量存在的肠道过程。具体地说，肠道对氯的吸收是目前研究的重点，这对水的吸收是很重要的。美国国家科学基金会之前资助的研究确定了一种新的氯离子吸收途径，在大多数鱼类中，这一途径至少占总吸收的50%。这种摄取氯的途径涉及将大量的碱分泌到肠腔中，但这种碱的排泄最终可能会导致鱼的酸碱平衡受到挑战。在海鱼身上，这一挑战是通过排泄一定比例的酸来维持正常的血液PH值来应对的。通过使用分子技术和对肠腔内细胞的研究，这项研究的目标是确定参与这一独特的氯离子吸收途径的特定蛋白质。此外，最近开发的设备，可以同时测定鱼肠道的耗氧量和离子传输，将被用来检验从摄入的海水中吸收液体具有高代谢成本的假设。通过这一研究课程，将培养研究生和本科生研究人员。此外，这项研究的结果将被纳入一门关于鱼类环境生物学的大学课程，并被纳入一门针对当地公立学校系统高中教师的环境健康课程，当地公立学校系统的人口结构高度多样化。

The salty marine environment is dehydrating and marine fish are left with seawater as the only source of hydration. In land-dwelling animals ingestion of seawater results in severe diarrhea which, in itself, is dehydrating. In contrast, marine fish are able to absorb fluids from ingested seawater and can successfully eliminate the associated salt gain. The present project aims to further characterize the intestinal processes that allow for these vertebrates to exist in abundance in oceanic environments. Specifically, uptake of chloride across the intestine, which is important for the absorption of water, is the focus of the present research. The PI's previous NSF funded research identified a novel pathway for chloride absorption, which in most fish accounts for at least 50% of the total uptake. This chloride uptake pathway involves the secretion of large quantities of base into the intestinal lumen, but excretion of this base could ultimately result in a challenge to the acid-base balance of the fish. This challenge is met in marine fish by excretion of a proportional amount of acid across their gills to maintain normal blood pH. Through the use of molecular techniques and studies of cells lining the intestinal lumen the goal of this research is to identify the specific proteins involved in this unique chloride uptake pathway. In addition, recently developed equipment, which allows for the determination of both oxygen consumption and ion transport by fish intestine, will be employed to test that hypothesis that absorption of fluid from ingested seawater has a high metabolic cost. Through the course of this research graduate and undergraduate researchers will be trained. In addition, the findings of this research will be incorporated into a university course about the environmental biology of fishes and into an environmental health curriculum targeted to high school teachers in the local public school system, which has a highly diverse demography.