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

咸的海洋环境正在脱水，海洋鱼类只剩下海水作为水合作用的唯一来源。陆地动物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，并可以成功地消除相关的盐的增加。本项目旨在进一步描述这些脊椎动物在海洋环境中大量存在的肠道过程。具体来说，通过肠道吸收氯，这是重要的水的吸收，是本研究的重点。PI之前的NSF资助的研究确定了一种新的氯化物吸收途径，在大多数鱼类中，氯化物吸收至少占总吸收量的50%。这种氯化物摄取途径涉及大量碱分泌到肠腔中，但这种碱的排泄最终可能导致对鱼的酸碱平衡的挑战。这一挑战是满足海鱼排泄的比例量的酸在他们的鳃，以保持正常的血液pH值。通过使用分子技术和研究细胞内衬肠腔，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，它允许确定耗氧量和离子运输的鱼肠，将被用来测试这一假设，即从摄入的海水中吸收液体具有很高的代谢成本。通过这项研究的过程中，研究生和本科生的研究人员将得到培训。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，并纳入一门针对当地公立学校系统高中教师的环境卫生课程，该系统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.