Intestinal Bicarbonate Secretion in Marine Teleost Fish

题目：海洋硬骨鱼的肠道碳酸氢盐分泌PI: Grosell， M.机构：迈阿密大学罗森斯蒂尔海洋与大气科学学院该项目研究海洋鱼类中盐和水平衡的一个新方面。与大多数其他脊椎动物一样，海洋鱼类的血浆渗透压维持在300 mOsm左右，远低于周围海水的渗透压（1000 mOsm）。鱼类饮用大量的海水，以取代扩散到环境中的水分流失。被吸收的海水在食道中被淡化，然后在肠道中吸收Na+和Cl-驱动水分吸收。最近的证据表明，肠道Cl-摄取的很大一部分是通过肠上皮顶端膜的Cl-/ HCO3-交换发生的，这一交换过程有助于两种离子的主动运输。PIs旨在描述分离肠上皮上Cl-摄取/HCO3-分泌系统的细胞机制，并评估其对完整动物整体Cl-和水吸收的贡献。高速率的HCO3-分泌导致高碱性肠液，这导致CaCO3在肠道中沉淀。这种沉淀的一个后果是降低肠道液体的渗透压，这被认为有助于水的吸收。通过肠道灌注不同成分的盐碱来进行沉淀操作，以检验这一假设。肠道大量的碱分泌虽然不参与酸碱平衡的动态调节，但却是与环境进行酸碱交换的重要组成部分。pi将研究肠道碱分泌的变化对不同环境盐度的响应如何通过肠外酸挤压来补偿。这项研究有很强的教育成分，涉及几名本科生和研究生。

Title: Intestinal bicarbonate secretion in marine teleost fish PI: Grosell, M. Institution: University of Miami Rosensteil School of Marine and Atmospheric SciencesThis project investigates a novel aspect of salt and water balance in marine fish. Like most other vertebrates, marine fish maintain plasma osmolality ~ 300 mOsm which is much lower than that of the surrounding seawater (~1000 mOsm). Fish drink copious amounts of seawater to displace diffusive water loss to their environment. The imbibed seawater is desalinized in the esophagus after which Na+ and Cl- absorption in the intestine drives water uptake. Recent evidence suggests that a substantial portion of this intestinal Cl- uptake occurs via Cl-/ HCO3- exchange across the apical membrane of the intestinal epithelium and that this exchange process contributes to active transport of both ions. The PIs will aim at characterizing the cellular mechanisms of this Cl- uptake/HCO3- secretion system on isolated intestinal epithelia and to evaluate its contribution to overall Cl- and water absorption absorption also in intact animals. The high rates of HCO3- secretion results in highly alkaline intestinal fluid, which leads to CaCO3 precipitation in the intestine. One consequence of this precipitation is reduced osmolality of the intestinal fluids, which is hypothesized to aid water absorption. Manipulations of the precipitation through intestinal perfusion with salines of different composition are being performed to test this hypothesis. Although the substantial intestinal base secretion is not involved in dynamic regulation of acid-base balance it forms an important component of acid-base exchange with the environment. The PIs will investigate how variations in intestinal base secretion in response to different ambient salinities may be compensated by extra-intestinal acid extrusion. The research has a strong educational component and involves several undergraduate and graduate students.