H+ NEUTRALIZATION AND C1- HOMEOSTASIS IN GASTRIC MUCOSA

胃粘膜中的 H 中和和 C1- 稳态

• 批准号: 2654513
• 负责人: DAVID I SOYBEL
• 金额: $ 20万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-02-01 至 2002-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2654513
• 关键词: acid base balance; ammonia; aspirin; basolateral membrane; bicarbonates; carbachol; chloride ion; fluorescent dye /probe; gastric mucosa; gastrins; gastrointestinal epithelium; gene expression; histamine; homeostasis; immunocytochemistry; indomethacin; intermolecular interaction; ion transport; laboratory rat; membrane transport proteins; microelectrodes; potassium ion; protein biosynthesis; sodium ion; western blottings

DESCRIPTION: (Adapted from investigator's abstract) This application represents a continuation of the principal investigator's FIRST Award. The long-term goal of this project is to evaluate, at the cellular level, the mechanisms that protect gastric mucosa from the damaging effects of luminal acid. Until recently, it was accepted that a Cl-/HCO3- exchanger, located in the basolateral cell membrane, is responsible for regulation of intracellular Cl- levels (aiCl) and intracellular pH (pHi) in surface cells and oxyntic cells. We recently found evidence to suggest that a basolateral Na-K-Cl cotransport process plays a dominant and previously unsuspected role in preserving intracellular Cl- levels of the surface cells and in regulating HCl secretion by oxyntic cells. These findings have altered the previous model and led to the following hypotheses: 1) a basolateral, HCO3--independent, Na-K-Cl cotransporter is the dominant mechanism for regulating aiCl of oxyntic cells and surface cells in Necturus gastric fundus during stimulation of acid secretion; 2) a complementary, Cl--independent mechanism of basolateral HCO3-extrusion is also present in the oxyntic cell and contributes significantly to the "alkaline tide" generated by high rates of acid secretion; 3) expression of basolateral transporters that are dominant in preserving aiCl and pHi in the oxyntic cells is regulated by the gastric neurohumoral milieu; 4) secretory activity of the oxyntic glands plays a major role in regulating cell pH and ion composition of the neighboring surface epithelial cells during high rates of acid secretion and during exposure to ulcerogenic conditions; and 5) the ammonium (NH4+) ion that is produced by the pathogen H. pylori may gain access to the cell via the Na-K-Cl cotransporter, leading to disturbances in both aiCl and pHi. Studies proposed in this application will address these hypotheses using intracellular microelectrode and fluorescence techniques for measuring pH and ion composition, and molecular methods for evaluating expression of membrane transporters. The specific aims of this application are organized into four parts. First, we will evaluate the relationship of the basolateral Cl--transporting processes and their implications for regulation of HCO3- transport and other protective functions in both surface cells and oxyntic cells in the mucosa of the gastric fundus of Necturus. Second, we will examine, in both amphibian and mammalian models, the effects of secretory agonists such as gastrin, histamine, carbachol in stimulating synthesis and expression of the basolateral HCO3- and Cl- transport systems in surface cells and oxyntic cells of gastric mucosa. Third, we will evaluate the effects of ulcerogens such as aspirin or indomethacin on activity and expression of basolateral Cl- transport systems in both surface cells and oxyntic cells. Finally, we will explore the interaction between ammonium (NH4+), which is produced by the bacterium Helicobacter pylori, and cell pH and Cl- homeostasis. Using these techniques, we hope to provide detailed information regarding activity and expression of transport processes that preserve ion composition and pH in gastric mucosal cells during acid secretion or exposure to ulcerogenic conditions.

描述：(改编自调查人员摘要)本申请 代表着首席调查员第一个奖项的延续。这个 该项目的长期目标是在细胞水平上评估 鲁米那对胃粘膜损伤的保护机制 酸。直到最近，人们还接受了位于 在基侧细胞膜上，负责调节 表面细胞的胞内氯离子水平(AICL)和胞内pH(Phi) 和含氧细胞。我们最近发现的证据表明，一个基底侧向 钠-钾-氯共转运过程起主导作用，这是以前未曾预料到的 在保持细胞表面细胞内氯离子水平和 氧合细胞调节HCl的分泌。这些发现改变了 以前的模型，并导致了以下假设：1)基底侧向， 不依赖HCO3的Na-K-Cl共转运体是 胃泌酸细胞和胃壁表面细胞的AICL调节 刺激胃酸分泌时的眼底；2)补充， 基侧HCO3-挤出的非CL-机理也存在于 含氧细胞，对“碱性潮汐”有重要贡献 由高排酸率产生；3)基底侧位表达 氧合酶中主要维持AICL和PHI的转运蛋白 细胞受胃神经体液环境的调节；4)分泌活动 在调节细胞的pH和离子方面起着主要作用。 高转移率时相邻表面上皮细胞的组成 胃酸分泌和暴露在溃疡形成的条件下；以及5) 幽门螺杆菌产生的NH4+离子可能会获得 通过Na-K-Cl共转运体进入细胞，导致细胞内 AICL和PHI。本申请中提出的研究将解决这些问题 基于细胞内微电极和荧光技术的假说 用于测量pH和离子组成，以及用于评估的分子方法 膜转运蛋白的表达。本申请的具体目的 分为四个部分。首先，我们将评估两国的关系 氯离子的基底侧向输送过程及其意义 调节两个表面的HCO3-运输和其他保护功能 癌肿胃底粘膜内的细胞和含氧细胞。 第二，我们将在两栖动物和哺乳动物模型中检验这种影响 胃泌素、组胺、氨基甲胆碱等分泌激动剂在刺激 碱侧HCO3-和Cl3-转运系统的合成与表达 在胃粘膜表面细胞和含氧细胞中。第三，我们将 评估阿司匹林或消炎痛等溃疡病原体对胃溃疡的影响 基侧氯离子转运系统在两个表面的活性和表达 细胞和含氧细胞。最后，我们将探讨两者之间的交互作用 幽门螺杆菌产生的铵(NH4+)，以及 细胞pH和氯离子动态平衡。使用这些技术，我们希望提供 关于运输活动和表述的详细信息 胃粘膜细胞中保持离子组成和pH的过程 在胃酸分泌或暴露在溃疡形成的条件下。