SODIUM INTAKE AND ANGIOTENSIN II IN MICROCIRCULATORY RAREFACTION

微循环稀薄中的钠摄入量和血管紧张素 II

• 批准号: 6564867
• 负责人: ANDREW S. GREENE
• 金额: $ 28.24万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6564867
• 关键词: angiogenesis; angiotensin II; dietary sodium; genetic strain; growth inhibitors; high performance liquid chromatography; histopathology; hormone receptor; immunocytochemistry; laboratory rat; microcirculation; neuropeptide receptor; nutrition related tag; polymerase chain reaction; protein localization; receptor expression; renin angiotensin system; salt intake; vascular resistance; video microscopy; western blottings

Project 5 examines the role of the angiotensin II in the anatomical loss of microvessels (rarefaction) that occurs in animals fed a high salt diet. He have shown that an elevation in sodium intake can trigger a series of events culminating in a substantial rarefaction throughout the microcirculation in normal rats. In the previous funding period we have demonstrated that rarefaction of the microcirculation can cause an increase in total peripheral resistance, reduced tissue perfusion, decreased oxygen delivery, and impaired organ function. Although the mechanism by which this occurs are not well understood, a number of key observations point to a role for the renin-angiotensin system in this effect. First, maintenance of ANGII at normal levels during periods of HS diet completely eliminates rarefaction. Second, elevated salt intake causes a decrease in microvascular AT/1 receptors which are growth stimulatory and an increase in the microvascular AT/2 receptors which are growth inhibitory. Third, ANGII infused either systematically at sub- pressor levels, or locally into the skeletal muscle interstitium, can induce significant micro-vessel growth. The present study will examine the hypothesis that during period of high slat intake, suppression of either local or circulating ANGII mediate rarefaction. We further hypothesize that actions and augment the rarefaction caused by ANGII suppression. Using a highly sensitive and specific method for the measurement of tissue ANGII that was developed in our laboratories, we have shown that the concentration of ANGII in microvessels of the cremaster muscle is at least 5 times that measured in plasma. To our knowledge this is some of the most direct evidence supporting a role for the local renin-angiotensin system in the microcirculation. The goal of this project is to explore the regulation of the local vascular renin-angiotensin system in the microcirculation and to determine its role in microvascular rarefaction. The role of ANGII in the remodeling of the microcirculation will be assessed in chronically instrumented rats using direct intravenous and local infusions of ANGII to precisely control circulating and local concentrations. Mechanisms of the local control of the renin gene expression will be studied in a unique set of congenic Dahl rat strains in which the R renin gene has been introgressed into the S rat genetic background. We will take advantage of the difference in the renin response in these two unique, genetically matched, strains of rats to test the hypothesis that modulation of the renin-angiotensin system is responsible for the rarefaction due to salt. The application of several exciting and novel techniques will enable examination of this hypothesis. Micro-vessel function will be evaluated in vivo using computer video microscopy. Morphological changes in the microcirculation triggered by salt will be evaluated using quantitative stereological techniques that we have developed and used extensively. Localization of angiotensin receptors in the microcirculation will be carried out using highly specific AT/1 and AT/2 antibodies for immune-histochemistry and immuno-blotting of protein isolated from microvessels dissected from skeletal muscle. The effects of salt intake and circulating levels of ANGII on the distribution of AT/1, and AT/2 mRNA and protein throughout the microcirculation will be determined using competitive RT-PCR, immuno-histochemistry and Western blots to determine if the expression of these receptors is regulated by ANGII. Finally, measurements of circulating and vascular ANGII levels by HPLC combined with local infusion of ANGII and ANGI and local blockade of ACE will determine if change in the locally acting angiotensin system plays a significant role in the remodeling of the microcirculation.

项目 5 检查血管紧张素 II 在解剖学损失中的作用 喂养高盐饮食的动物中发生的微血管（稀疏）。 他已经证明钠摄入量的增加会引发一系列的 事件最终导致整个地区的严重稀疏 正常大鼠的微循环。在之前的资助期间，我们有 研究表明，微循环稀薄会导致 总外周阻力增加，组织灌注减少， 氧气输送减少，器官功能受损。虽然 发生这种情况的机制尚不清楚，一些关键 观察结果表明肾素-血管紧张素系统在此过程中发挥作用 影响。首先，HS期间ANGII维持在正常水平 饮食完全消除稀疏。二、盐摄入量增加 导致微血管 AT/1 受体减少，从而促进生长 刺激并增加微血管 AT/2 受体 生长抑制。第三，ANGII 系统地注入亚 升压水平，或局部进入骨骼肌间质，可以 诱导显着的微血管生长。本研究将检验 假设在高板条摄入期间，抑制任一 局部或循环的 ANGII 介导稀疏。我们进一步假设 这种作用并增强了 ANGII 抑制引起的稀疏性。 使用高度灵敏且特异的方法测量组织 我们实验室开发的 ANGII，我们已经证明 提睾肌微血管中 ANGII 的浓度至少为 是血浆测量值的 5 倍。据我们所知，这是最 支持局部肾素-血管紧张素系统作用的直接证据 在微循环中。该项目的目标是探索 局部血管肾素-血管紧张素系统的调节 微循环并确定其在微血管稀疏中的作用。 ANGII 在微循环重塑中的作用将是 使用直接静脉注射和长期仪器化大鼠进行评估 ANGII 的局部输注可精确控制循环和局部 浓度。肾素基因的局部控制机制 将在一组独特的同源 Dahl 大鼠品系中研究表达 R肾素基因已渗入S大鼠基因中 背景。我们将利用肾素反应的差异 在这两种独特的、基因匹配的老鼠品系中测试 假设肾素-血管紧张素系统的调节负责 由于盐导致的稀疏。几个令人兴奋的应用 新技术将能够检验这一假设。微血管 将使用计算机视频显微镜在体内评估功能。 盐引起的微循环形态变化 使用我们拥有的定量体视学技术进行评估 得到了广泛的开发和应用。血管紧张素受体的定位 微循环将使用高度特异性的 AT/1 进行， 用于蛋白质免疫组织化学和免疫印迹的 AT/2 抗体 从骨骼肌解剖的微血管中分离出来。的影响 盐摄入量和 ANGII 循环水平对 AT/1 分布的影响， 整个微循环中的 AT/2 mRNA 和蛋白质将被 使用竞争性 RT-PCR、免疫组织化学和 Western 测定 印迹以确定这些受体的表达是否受调节 ANGII。最后，通过测量循环和血管 ANGII 水平 HPLC联合局部输注ANGII和ANGI以及局部阻断 ACE 将确定局部作用的血管紧张素系统是否发生变化 在微循环重塑中发挥着重要作用。