H+ NEUTRALIZATION AND C1- HOMEOSTASIS IN GASTRIC MUCOSA

描述：（改编自研究者摘要）本申请 代表了首席研究员的第一个奖项的延续。 的 该项目的长期目标是在细胞水平上评估 保护胃粘膜免受鲁米那损伤作用的机制 酸 直到最近，人们才接受Cl-/HCO 3-交换器，位于 在基底外侧细胞膜上，负责调节 表面细胞的细胞内Cl-水平（aiCl）和细胞内pH（pHi） 和泌酸细胞。 我们最近发现的证据表明 Na-K-Cl共转运过程起着主导作用，这在以前是未知的 在保持细胞内Cl-水平的表面细胞， 通过泌酸细胞调节HCl分泌。 这些发现改变了 先前的模型并导致以下假设：1）基底外侧， HCO 3-非依赖性Na-K-Cl协同转运蛋白是 胃泌酸细胞和表面细胞aiCl的调节 在刺激酸分泌期间的眼底; 2）互补的， 基底外侧HCO 3-排出的Cl-非依赖性机制也存在于 泌酸细胞，并对“碱潮”有重要贡献 产生的高速率的酸分泌; 3）表达基底外侧 在保持胃酸分泌中aiCl和pHi中占主导地位的转运蛋白 细胞受胃神经体液环境的调节; 4）分泌活动 在调节细胞pH值和离子浓度方面起着重要作用 在高速率的细胞增殖过程中， 酸分泌和暴露于溃疡性条件期间;和5） 由病原体H产生的铵（NH 4+）离子。幽门螺杆菌可能获得 通过Na-K-Cl协同转运蛋白进入细胞，导致细胞内 aiCl和pHi两者。 本申请中提出的研究将解决这些问题 利用细胞内微电极和荧光技术的假说 用于测量pH值和离子组成，以及用于评估 膜转运蛋白的表达。 本申请的具体目的是 分为四个部分。 首先，我们将评估 基底外侧氯离子转运过程及其对 调节HCO 3-运输和两个表面的其他保护功能 细胞和泌酸细胞。 其次，我们将在两栖动物和哺乳动物模型中研究 分泌激动剂如胃泌素、组胺、卡巴胆碱 基底外侧HCO 3-和Cl-转运系统的合成和表达 胃粘膜的表面细胞和泌酸细胞。 三是 评价溃疡剂如阿司匹林或吲哚美辛对 基底外侧Cl-转运系统的活性和表达 细胞和泌酸细胞。 最后，我们将探讨 铵（NH 4+），其由细菌幽门螺杆菌产生，和 细胞pH和Cl-稳态。 利用这些技术，我们希望提供 关于交通活动和表达的详细信息 保持胃粘膜细胞中离子组成和pH的过程 在酸分泌或暴露于溃疡条件期间。

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.