Intestinal Bicarbonate Secretion in Marine Teleost Fish

标题：海洋硬骨鱼的肠道碳酸氢盐分泌PI：Grosell，M.研究所：迈阿密大学罗森斯泰尔海洋和大气科学学院这个项目研究了海洋鱼类盐和水平衡的一个新方面。与大多数其他脊椎动物一样，海鱼的血浆渗透压维持在300mOsm左右，远低于周围海水的渗透压(1000mOsm)。鱼吸收大量的海水，以取代扩散到环境中的水分损失。被吸入的海水在食道中被淡化，之后肠道中的Na和Cl-吸收驱动水的吸收。最近的证据表明，很大一部分肠道的氯离子摄取是通过跨越肠上皮顶膜的氯离子/HCO3-交换进行的，这一交换过程有助于这两种离子的主动运输。PI将致力于研究这一氯离子摄取/HCO3-分泌系统在离体肠上皮细胞上的细胞机制，并评估其对完整动物整体的氯离子和水吸收的贡献。HCO3的高分泌率导致肠液高度碱性，从而导致CaCO3在肠道中沉淀。这种沉淀的一个后果是降低了肠液的渗透压，这被认为有助于水的吸收。通过肠道灌流不同成分的生理盐水对降水的处理正在进行，以检验这一假设。虽然大量的肠碱分泌不参与酸碱平衡的动态调节，但它构成了与环境进行酸碱交换的重要组成部分。PI将研究不同环境盐度下肠道底部分泌的变化如何通过肠外排酸来补偿。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.