SENSING PH AT THE GASTRIC SURFACE

胃必须在胃上皮分泌的HCl中存活。这种挑战由于化合物（例如非甾体抗炎药）或微生物（幽门螺杆菌）的频繁存在而加剧，这些化合物或微生物会损害胃对酸的屏障，从而在屏障被破坏时导致溃疡。一个碱性明胶凝胶层是胃防御的第一道防线：保护胃上皮细胞免受来自管腔的酸的反向扩散。我们已经开发出一种独特的方法来非侵入性地测量体内胃表面的pH值。使用共聚焦显微镜，我们已经成像的amuclidae碱性层，它转换成一个酸层时，管腔pH值改变到发现在进食胃的值。我们的研究结果表明，胃表面pH值调节，其中包括控制表面pH值的转运蛋白的实质性变化的新模型。我们的目标是定义调节胃腔pH值传感和表面pH值调节的元素。主要使用在体内共聚焦显微镜的大鼠或小鼠胃，我们的第一个目标将定义胃的基本要求，以感知和响应管腔pH值。我们将a）定义的时间和位置的管腔pH值变化所需的转换从碱到酸分泌，和B）测试管腔营养物质和缓冲液在表面pH值调节的作用。在第二个目标中，我们将质疑哪些分子是介导胃酸和碱分泌的综合调节的管腔pH刺激的换能器。我们将集中在生长抑素，前列腺素E2和辣椒素敏感的传入神经含有CGRP的作用。生长抑素的作用将使用生长抑素2型受体（SST 2）的选择性拮抗剂和激动剂与SST 2敲除小鼠的平行研究进行分析。前列腺素合成的作用将使用已知的环氧合酶（考克斯）亚型的选择性抑制剂，与考克斯-1和考克斯-2敲除小鼠的平行研究。辣椒素敏感的传入将使用香草酸受体激动剂，CGRP受体激动剂和拮抗剂进行分析，与化学去传入动物的平行研究。第三个目标将询问胃粘膜损伤如何破坏表面pH调节。我们将通过双光子显微镜在胃上皮中产生显微病变。使用这种新的局灶性胃损伤模型，我们将跟踪表面pH调节的中断和真实的组织修复过程。我们将询问阿司匹林，临床粘膜损伤的主要原因，是否通过破坏正常和COX基因敲除小鼠的管腔pH传感和表面pH调节来削弱胃屏障。我们将确定阿司匹林是否会影响双光子显微镜所造成的局灶性病变的修复。研究结果将整合对胃防御与酸碱分泌调节的理解。

The stomach must survive HCl secreted by the gastric epithelium. This challenge is heightened by the frequent presence of compounds (e.g. non-steroidal anti-inflammatory drugs) or organisms (Helicobacter pylori) which compromise the gastric barrier to acid, leading to ulcers when the barrier is breached. An alkaline juxtamucosal gel layer is the first line of gastric defense: acting to protect the gastric epithelium from back-diffusion of acid from the lumen. We have developed a unique approach to non-invasively measure pH at the gastric surface in vivo. Using confocal microscopy, we have imaged a juxtamucosal alkaline layer, which converts to an acid layer when luminal pH is changed to values found in the fed stomach. Our results suggest a new model of gastric surface pH regulation, which includes a substantial change in the transporters that control surface pH. Our objective is to define the elements regulating luminal pH sensing and surface pH regulation in the stomach. Using primarily in vivo confocal microscopy of rat or mouse stomach, our first aim will define fundamental requirements for the stomach to sense and respond to luminal pH. We will a) define the timing and location of luminal pH change required for conversion from alkali to acid secretion, and b) test the role of luminal nutrients and buffers in surface pH regulation. In the second aim, we will question which molecules are transducers of the luminal pH stimulus that mediate the integrated regulation of both gastric acid and alkali secretion. We will focus on the role of somatostatin, PGE2, and capsaicin-sensitive afferent nerves containing CGRP. The role of somatostatin will be analyzed using antagonists and agonists selective for the somatostatin type 2 receptor (SST2) with parallel studies of SST2-knockout mice. The role of prostaglandin synthesis will be approached using selective inhibitors of known cycloxygenase (COX) isoforms, with parallel studies of COX-1 and COX-2 knockout mice. Capsaicin-sensitive afferents will be analyzed using vanilloid receptor agonists, CGRP receptor agonists and antagonists, with parallel studies of chemically deafferented animals. The third aim will ask how gastric mucosal damage disrupts surface pH regulation. We will generate microscopic lesions in the gastric epithelium by two-photon microscopy. Using this new model of focal gastric damage, we will follow the disruptions in surface pH regulation and the tissue repair process in real time. We will ask if aspirin, a major cause of clinical mucosal damage, weakens the gastric barrier by disruption of luminal pH sensing and surface pH regulation in normal and COX-knockout mice. We will determine if aspirin affects the repair of focal lesions created by two-photon microscopy. Results will integrate understanding of gastric defense with regulation of acid and alkali secretion.