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

咸的海洋环境正在脱水，海水是海洋鱼类唯一的水合来源。陆生动物摄取海水会导致严重的腹泻，这本身就是脱水。相比之下，海鱼能够从摄入的海水中吸收液体，并能成功地消除相关的盐增益。目前的项目旨在进一步表征肠道过程，使这些脊椎动物能够在海洋环境中大量存在。具体来说，氯离子在肠道中的吸收对水的吸收很重要，这是本研究的重点。该研究所之前由美国国家科学基金会资助的研究发现了一种新的氯化物吸收途径，这种途径在大多数鱼类中至少占总吸收量的50%。这种氯化物摄取途径涉及将大量碱分泌到肠腔中，但这种碱的排泄最终可能导致对鱼类酸碱平衡的挑战。这一挑战是通过海洋鱼类的鳃排泄成比例的酸来维持正常的血液ph值来解决的。通过使用分子技术和研究肠腔内的细胞，本研究的目标是确定参与这种独特的氯化物摄取途径的特定蛋白质。此外，最近开发的设备可测定鱼肠的耗氧量和离子运输，将用于验证从摄入的海水中吸收液体具有高代谢成本的假设。通过本研究课程将培养研究生和本科生的研究人员。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，以及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.