PARACRINE REGULATION OF RENAL FUNCTION BY DOPAMINE IN NORMOTENSIVE AND HYPERT

正常血压和高血压状态下多巴胺对肾功能的旁分泌调节

• 批准号: 7608299
• 负责人: ARUNA R NATARAJAN
• 金额: $ 1.68万
• 依托单位: CHILDREN'S RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-12-01 至 2007-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7608299
• 关键词: Adrenal Glands; Affect; Agonist; Aldosterone Synthase; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Angiotensins; Award; Basic Science; Biology; Biophysics; Blood Pressure; Blood Vessels; Clinic; Clinical Research; Computer Retrieval of Information on Scientific Projects Database; Condition; Coronary; Coronary artery; Creatinine; Crossover Design; Development; Diet; Disease; Doctor of Philosophy; Dopamine; Dopamine Agonists; Dopamine D1 Receptor; Dopamine Receptor; Double-Blind Method; Effective Renal Plasma Flow; Electrolyte Balance; Enalapril; Enzyme Inhibition; Equilibrium; Essential Hypertension; Excretory function; Fenoldopam; Funding; G-Protein-Coupled Receptors; GRK4 gene; Genetic; Genetic Polymorphism; Genetic Variation; Genotype; Glomerular Filtration Rate; Grant; Hour; Human; Hypertension; In Vitro; Infusion procedures; Institution; Intake; Internal Medicine; Intervention; Kidney; Liquid substance; Lithium; Measures; Mediating; Mentors; Methods; NCI Scholars Program; National Center for Research Resources; Natriuresis; Neurotransmitters; Pathogenesis; Peptidyl-Dipeptidase A; Physiology; Placebo Control; Placebos; Potassium Channel; Preparation; Protocols documentation; Proximal Kidney Tubules; Randomized; Receptor Signaling; Receptor, Angiotensin, Type 1; Recruitment Activity; Regulation; Renal function; Renin; Renin-Angiotensin System; Reporting; Research; Research Design; Research Personnel; Resources; Role; Signal Pathway; Smooth Muscle Myocytes; Sodium; Sodium Chloride; Sodium-Restricted Diet; Source; System; Testing; Tubular formation; United States National Institutes of Health; Universities; Urine; Variant; Week; Work; abstracting; adducin; computerized; day; di-n-hexyl sulfosuccinate; genetic variant; human GPRK2L protein; human subject; in vivo; normotensive; paracrine; posters; receptor; response; salt intake; salt sensitive; saluretic; sex; urinary; volunteer

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. As of 2/07/06 Background Blood pressure is influenced by dietary salt intake; indeed 30% of people with normal blood pressure and 50-70% of people with hypertension are salt-sensitive. Dopamine, a well-known neurotransmitter, has been identified as an important modulator of blood pressure, sodium balance, renal function and adrenal function through an independent, paracrine effect on the kidneys. Angiotensin II is also an important paracrine regulator of sodium balance and blood pressure. The dopaminergic and renin-angiotensin systems have been shown to interact in vitro and in vivo. In this protocol, we will study the effects of inhibition of the renin-angiotensin system on the effects of stimulation of the dopaminergic system, in salt loaded and salt depleted states, in normotensive and hypertensive human subjects. We will correlate these effects with the presence or absence of recently described genetic polymorphisms in the post-receptor signaling pathway of the dopamine receptor in the proximal tubule of the kidney, specifically the G protein- coupled receptor kinase, GRK4. Together, this information will help us better understand the effects of salt and genotype on the pathogenesis of essential hypertension, a disease that affects more than a billion people worldwide. Hypothesis The angiotensin converting enzyme (ACE) inhibitor, Enalapril, augments natriuresis caused by D1 receptor stimulation, in normotensive and hypertensive human subjects, in salt loaded and salt depleted states. These effects are reduced in subjects who have polymorphisms of the G protein-coupled receptor kinase, GRK4. The augmentation of natriuresis is increased in hypertensive subjects with increased renin-angiotensin tone. Methods/Study Design This is a double blind, placebo-control, crossover design. 20 normotensive volunteers and 28 hypertensive subjects, recruited from an Internal Medicine clinic, of both sexes, between 18-55 years will participate in the study. They will all have 5 days each of low (50meq/day) sodium, and moderate (300meq/day) sodium diet, 4 weeks apart. Each subject will have four interventions applied in sequence, the first intervention being randomized as per a computerized plan. The four interventions are: high salt diet + placebo, high salt diet + Enalapril, low salt diet +placebo, and low salt diet + Enalapril. All subjects will undergo renal function tests, before, during and after a 3-hour infusion of Fenoldopam, which is a selective dopamine (D1) receptor agonist. We will measure urinary sodium excretion, and, by measuring creatinine , PAH and lithium clearance, we will estimate glomerular filtration rate, effective renal plasma flow, and proximal tubular sodium reabsorption of sodium respectively. All subjects will be genotyped for the common polymorphisms associated with the development of essential hypertension, specifically, GRK4, alpha adducin, aldosterone synthase, and genetic variants of the human D5 receptor. Statistical Analysis We will compare the change in the excretion of sodium from baseline between Enalapril/placebo treatments, and between low and moderate salt diet periods, in each subject. Urinary sodium excretion will be studied separately in normotensive and hypertensive groups, and then compared. We will genotype all subjects and using single locus and multi loci analyses to determine differences in the occurrence of polymorphisms between hypertensive and normotensive subjects. Anticipated Results In normotensive subjects, inhibition of angiotensin II formation by ACE inhibition will augment Fenoldopam -induced natriuresis in the moderate sodium diet, and also in the low sodium diet, where normally the renin-angiotensin system has an important sodium-retaining role. In hypertensive subjects, where the natriuretic response to Fenoldopam has been reported to be impaired, we anticipate that Enalapril will enhance natriuresis to a greater extent in those subjects with increased renin-angiotensin tone. Basic Science Component We study the function of dopamine, specifically dopaminergic post receptor signaling pathways in the human coronary vascular smooth muscle cells in humans, specifically its possible role in activation of big potassium channels, abnormalities in which may contribute to the increase in myogenic vascular tone seen in hypertension. This work has led to a first author abstract entitled 'D5 receptor mediates Dopamine effects on Big KCa channels in human coronary artery smooth muscle cells' Aruna Natarajan, Guichun Han, Richard White and Pedro Jose, which will be presented as a poster at the Experimental Biology meeting in April 2006. This work will comprise Aruna Natarajan's thesis report for a PhD in Physiology and Biophysics at Georgetown University, currently in preparation. 3. Please provide scientific progress achieved to date (since last year's report if applicable): Initial abstract Dopamine is a well-known neurotransmitter, with paracrine effects on the kidney that have recently been elucidated. These effects result in natriuresis in response to a sodium load, mediated by a G-protein coupled receptor, the D1 receptor. Post-receptor signaling pathways have been found to be impaired in people with salt sensitive hypertension, attributed to a polymorphism of a G-protein coupled receptor kinase, GRK4. This study aims to elucidate the interaction between the renal dopaminergic system and the renin-angiotensin system (RAS) in salt-loaded and depleted states, by studying the effect of angiotensin converting enzyme (ACE) inhibition on the effect of Fenoldopam, a D-1 receptor agonist on salt excretion in the urine. The study will correlate these effects with the presence or absence of genetic polymorphisms of GRK4, aldosterone synthase, alpha-adducin and other polymorphisms, all of which have been described in people with salt-sensitive hypertension. This study will help us understand the interactions of salt, dopamine, RAS and genetic makeup in the pathogenesis of essential hypertension. SPECIFIC AIMS: This is an investigator-initiated study supported by the mentored Clinical Research Scholar Program Award, Grant RR 17613, from the NCRR, NIH, DHSS. The dopaminergic system has a major regulatory effect on fluid and electrolyte balance and blood pressure. The objective of this project is to determine the interaction of the renal dopaminergic and RAS in the regulation of sodium excretion during varying amounts of sodium intake. The specific aims are to determine: 1. The effect of sodium intake on the interaction between the RAS and D1 dopamine receptors on sodium excretion. 2. The effect of GRK4 gene variants on the natriuretic response to D1 dopamine receptor agonist and its modulation by ACE inhibition. Hypothesis: The natriuretic effect of D1 dopamine receptors, which is best manifest under conditions of sodium loading is antagonized by the antinatriuretic effect of AT1 angiotensin receptors. In essential hypertension the natriuretic effect of D1 receptors is impaired because of activating variants of GRK4 while the antinatriuretic effect of AT1 receptors is enhanced. The overall hypothesis is that ACE inhibition augments the natriuresis caused by D1 receptor stimulation in normotensive subjects, only in the salt loaded state. These effects are reduced in those subjects with GRK4 gene variants, in hypertensive subjects.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目及 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 截至 2006 年 2 月 7 日 背景 血压受膳食盐摄入量的影响；事实上，30% 的血压正常的人和 50-70% 的高血压患者对盐敏感。 多巴胺是一种众所周知的神经递质，通过对肾脏产生独立的旁分泌作用，已被认为是血压、钠平衡、肾功能和肾上腺功能的重要调节剂。血管紧张素 II 也是钠平衡和血压的重要旁分泌调节剂。多巴胺能系统和肾素-血管紧张素系统已被证明在体外和体内相互作用。在本协议中，我们将研究在正常血压和高血压人类受试者中，在盐负荷和盐耗尽状态下，抑制肾素-血管紧张素系统对刺激多巴胺能系统的影响。我们将把这些影响与最近描述的肾近曲小管多巴胺受体后信号传导通路（特别是 G 蛋白偶联受体激酶 GRK4）的受体后信号通路中是否存在遗传多态性相关联。这些信息将帮助我们更好地了解盐和基因型对原发性高血压发病机制的影响，原发性高血压是一种影响全球超过十亿人的疾病。 假设 血管紧张素转换酶 (ACE) 抑制剂依那普利可增强血压正常和高血压的人体受试者在盐负荷和盐消耗状态下由 D1 受体刺激引起的尿钠排泄。在具有 G 蛋白偶联受体激酶 GRK4 多态性的受试者中，这些影响会减弱。随着肾素-血管紧张素张力的增加，高血压患者的尿钠排泄也会增加。 方法/研究设计 这是双盲、安慰剂对照、交叉设计。从内科诊所招募的 20 名血压正常志愿者和 28 名高血压受试者（男女不限，年龄在 18 至 55 岁之间）将参与这项研究。他们将分别接受 5 天的低钠（50meq/天）和中度（300meq/天）钠饮食，间隔 4 周。每个受试者将依次接受四次干预，第一次干预根据计算机化计划随机进行。四种干预措施是：高盐饮食+安慰剂、高盐饮食+依那普利、低盐饮食+安慰剂、低盐饮食+依那普利。所有受试者将在输注非诺多泮（一种选择性多巴胺 (D1) 受体激动剂）3 小时之前、期间和之后接受肾功能测试。我们将测量尿钠排泄，并通过测量肌酐、PAH 和锂清除率，我们将分别估计肾小球滤过率、有效肾血浆流量和近端肾小管钠重吸收。 所有受试者都将进行与原发性高血压相关的常见多态性基因分型，特别是GRK4、α内收蛋白、醛固酮合酶和人类D5受体的遗传变异。 统计分析 我们将比较每个受试者依那普利/安慰剂治疗之间以及低盐和中盐饮食期间钠排泄相对于基线的变化。将分别研究正常血压组和高血压组的尿钠排泄，然后进行比较。 我们将对所有受试者进行基因分型，并使用单基因座和多基因座分析来确定高血压和正常血压受试者之间多态性发生的差异。 预期结果 在血压正常的受试者中，通过ACE抑制来抑制血管紧张素II的形成将增强中度钠饮食中非诺多泮诱导的尿钠排泄，并且在低钠饮食中也是如此，其中肾素-血管紧张素系统通常具有重要的钠保留作用。据报道，在高血压受试者中，对非诺多泮的利尿钠反应受损，我们预计依那普利将在肾素-血管紧张素张力增加的受试者中更大程度地增强利尿钠。 基础科学部分 我们研究多巴胺的功能，特别是人类冠状血管平滑肌细胞中的多巴胺能后受体信号通路，特别是它在激活大钾通道中的可能作用，其中的异常可能导致高血压中肌源性血管张力的增加。这项工作产生了题为第一作者的摘要 “D5 受体介导多巴胺对人冠状动脉平滑肌细胞大 KCa 通道的影响”Aruna Natarajan、Guichun Han、Richard White 和 Pedro Jose，该成果将在 2006 年 4 月的实验生物学会议上作为海报展示。这项工作将包括Aruna Natarajan 的乔治城大学生理学和生物物理学博士学位论文报告目前正在准备中。 3. 请提供迄今为止取得的科学进展（自去年的报告以来，如果适用）： 初始摘要 多巴胺是一种众所周知的神经递质，最近已阐明对肾脏的旁分泌作用。这些效应导致钠负荷引起的尿钠排泄，由 G 蛋白偶联受体（D1 受体）介导。研究发现，盐敏感性高血压患者的受体后信号通路受损，这是由于 G 蛋白偶联受体激酶 GRK4 的多态性所致。 本研究旨在通过研究血管紧张素转换酶（ACE）抑制对非诺多泮（一种 D- 药物）作用的影响，阐明在盐负荷和耗尽状态下肾脏多巴胺能系统与肾素血管紧张素系统（RAS）之间的相互作用。 1 受体激动剂对尿液中盐的排泄。该研究将这些影响与 GRK4、醛固酮合酶、α-内收蛋白和其他多态性的遗传多态性的存在或不存在相关联，所有这些都在盐敏感性高血压患者中得到了描述。这项研究将帮助我们了解盐、多巴胺、RAS 和基因组成在原发性高血压发病机制中的相互作用。 具体目标： 这是一项由研究者发起的研究，得到 NCRR、NIH、DHSS 指导的临床研究学者计划奖（Grant RR 17613）的支持。多巴胺能系统对液体和电解质平衡以及血压具有重要的调节作用。该项目的目的是确定在不同钠摄入量期间肾多巴胺能和 RAS 在调节钠排泄中的相互作用。 具体目标是确定： 1.钠摄入量对RAS和D1多巴胺受体之间相互作用对钠排泄的影响。 2.GRK4基因变异对D1多巴胺受体激动剂的利尿钠反应的影响及其通过ACE抑制的调节。 假设：D1 多巴胺受体的利尿钠作用在钠负荷条件下最为明显，但会被 AT1 血管紧张素受体的抗利尿钠作用所拮抗。 在原发性高血压中，由于 GRK4 的激活变体，D1 受体的利钠作用受损，而 AT1 受体的抗利尿作用增强。 总体假设是，ACE 抑制会增强血压正常受试者中 D1 受体刺激引起的尿钠排泄，仅在盐负荷状态下有效。在患有 GRK4 基因变异的高血压受试者中，这些影响会减弱。