Regulation of the Renal Microcirculation by the Connecting Tubule

连接小管对肾脏微循环的调节

• 批准号: 7766928
• 负责人: Oscar A. Carretero
• 金额: $ 32.63万
• 依托单位: HENRY FORD HEALTH SYSTEM
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-07 至 2012-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7766928
• 关键词: AGTR2 gene; Accounting; Acids; Amiloride; Angiotensin II; Angiotensinogen; Arachidonic Acids; Arts; Blood; Bradykinin; Chelating Agents; Cyclic AMP; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diffuse; Dilatation - action; Distal; Eicosanoids; Equilibrium; Feedback; Furosemide; Glomerular Filtration Rate; Guanylate Cyclase; Hydrochlorothiazide; Hypertension; In Vitro; Kidney; Kinins; Macula densa; Measures; Mediating; Microcirculation; Micropuncture; Morphology; Mus; NADPH Oxidase; Natriuresis; Nephrons; Nitric Oxide; Nitric Oxide Synthase; Norepinephrine; Perfusion; Phospholipase; Physiological; Play; Preparation; Process; Prostaglandins; Protein Isoforms; Protein Kinase Inhibitors; Regulation; Renal function; Renin; Renin-Angiotensin System; Reporting; Resistance; Reverse Transcriptase Polymerase Chain Reaction; Role; Side; Signal Transduction; Soluble Guanylate Cyclase; Stimulus; Techniques; Testing; Thromboxane A2; Tubular formation; Vascular resistance; Vasoconstrictor Agents; Vasodilation; acetovanillone; arteriole; benzamil; channel blockers; epithelial Na+ channel; in vivo; inhibitor/antagonist; insight; kidney cortex; kidney vascular structure; novel; pressure; protein kinase inhibitor; receptor; response; vasoconstriction

DESCRIPTION (provided by applicant): In hypertension the pressure natriuresis set point is shifted to a higher pressure, due to an increase in both renal vascular resistance and Na+ reabsorption. The afferent arterioles (Af-Art) and efferent arterioles account for most renal vascular resistance; they control glomerular filtration rate (GFR) and peritubular pressure, and consequently renal function. Af-Art resistance is regulated by factors similar to those that control other arterioles; in addition, the Af-Art is also controlled by tubuloglomerular feedback (TGF). TGF operates via the macula densa, which senses increases in NaCl and sends a signal that constricts the Af-Art. We have evidence that increasing NaCl delivery to the connecting tubule (CNT) dilates the Af-Art, and that this dilatation can be blocked by inhibitors of Na+ transport. We refer to the cross-talk between the CNT and Af-Art as connecting tubule glomerular feedback (CTGF). Here we propose to study CTGF both in vitro and in vivo to determine its physiological role and the mechanisms by which Na+ causes CTGF. We will also study the regulation of CTGF by nitric oxide (NO) and the tubular renin-angiotensin system (RAS), since both NO synthase and renin and angiotensinogen are expressed in the nephron. In vitro and in vivo we propose to test the general hypothesis that Na+ reabsorption by the connecting tubule induces the release of arachidonic acid metabolites that diffuse to and promote dilatation of the Af-Art (CTGF response). Thus CTGF antagonizes vasoconstrictor stimuli such as TGF. The tubular RAS potentiates CTGF by stimulating Na+ transport by the CNT, while NO blunts CTGF by inhibiting this process. We will test this general hypothesis in four Aims. Aim I will test whether an increase in Na+ reabsorption in the CNT causes an increase in intracellular Ca++ via the Na+/ Ca++ exchanger, which results in Ca++-mediated activation of phospholipases, release of arachidonic acid, and formation of eicosanoids which diffuse to the Af-Art and cause dilatation. Aim II will test whether in vivo, CTGF opposes the vasoconstrictor effect of TGF and whether in the absence of TGF, CTGF causes Af-Art dilatation. Aim III will test whether NO produced by NOS 3 in the CNT decreases CTGF by blocking Na+ transport by ENaC via activation of guanylyl cyclase, increasing cGMP, activating cGMP-dependent protein kinase, and reducing cAMP. Aim IV will test whether the tubular RAS via Ang II and the AT1 receptor enhances CTGF directly by acting on ENaC and indirectly by stimulating the release of O2- via NADPH oxidase. This will be the first study to determine the role of the renal connecting tubule in the regulation of afferent arteriole resistance and glomerular filtration rate. This is a novel mechanism that will provide new insights on the regulation of renal function.

描述（由申请人提供）：在高血压中，由于肾血管阻力和Na+重吸收的增加，压力钠排泄设定点转移至更高的压力。传入小动脉 (Af-Art) 和传出小动脉是肾血管阻力的主要来源；它们控制肾小球滤过率（GFR）和肾小管周围压力，从而控制肾功能。 Af-Art 抵抗力受到与控制其他小动脉类似的因素的调节。此外，Af-Art还受肾小球反馈（TGF）控制。 TGF 通过致密斑起作用，致密斑感知 NaCl 的增加并发出收缩 Af-Art 的信号。我们有证据表明，增加 NaCl 向连接小管 (CNT) 的输送会扩张 Af-Art，并且这种扩张可以被 Na+ 转运抑制剂阻断。我们将 CNT 和 Af-Art 之间的串扰称为连接小管肾小球反馈 (CTGF)。在这里，我们建议在体外和体内研究 CTGF，以确定其生理作用以及 Na+ 引起 CTGF 的机制。我们还将研究一氧化氮 (NO) 和肾小管肾素-血管紧张素系统 (RAS) 对 CTGF 的调节，因为 NO 合酶以及肾素和血管紧张素原均在肾单位中表达。我们建议在体外和体内测试一般假设，即连接小管对 Na+ 的重吸收会诱导花生四烯酸代谢物的释放，这些代谢物扩散到 Af-Art 并促进 Af-Art 的扩张（CTGF 反应）。因此，CTGF 拮抗血管收缩刺激，例如 TGF。肾小管 RAS 通过刺激 CNT 的 Na+ 转运来增强 CTGF，而 NO 通过抑制这一过程来减弱 CTGF。我们将在四个目标中检验这个一般假设。目的 我将测试 CNT 中 Na+ 重吸收的增加是否会通过 Na+/Ca++ 交换器导致细胞内 Ca++ 增加，从而导致 Ca++ 介导的磷脂酶激活、花生四烯酸释放以及类二十烷酸的形成，后者扩散到 Af-Art 并导致扩张。 Aim II 将测试体内 CTGF 是否对抗 TGF 的血管收缩作用，以及在没有 TGF 的情况下，CTGF 是否会导致 Af-Art 扩张。目标 III 将测试 CNT 中 NOS 3 产生的 NO 是否通过激活鸟苷酸环化酶、增加 cGMP、激活 cGMP 依赖性蛋白激酶和减少 cAMP 来阻断 ENaC 的 Na+ 转运，从而降低 CTGF。 Aim IV 将测试肾小管 RAS 是否通过 Ang II 和 AT1 受体直接作用于 ENaC 以及通过 NADPH 氧化酶刺激 O2- 的释放来间接增强 CTGF。这将是第一项确定肾连接小管在传入小动脉阻力和肾小球滤过率调节中的作用的研究。这是一种新的机制，将为肾功能的调节提供新的见解。