Role of the kidneys in hypertension: paracrine actions of NO in the renal medulla

描述（由申请人提供）：高血压困扰着大约1/3的美国人口。肾脏通过调节细胞外容积在血压调节中起重要作用。肾一氧化氮（NO）在细胞外容积调节中起重要作用，从而调节血压。抑制肾NO的产生一般和肾髓质中的特异性引起高血压。后者是由于髓质血流和肾单位转运的变化。在肾髓质中，NO扩张直小血管周细胞以增加髓质血流量。至少有一部分NO来自Henle环（塔尔）的相邻的粗升支。自由扩散被认为是NO离开塔尔并进入周细胞的主要机制。然而，我们最近发现，水通道蛋白-1（AQP-1）运输NO跨细胞膜的速度比自由扩散快4倍，并且AQP-1依赖的NO运输是内皮诱导的胸主动脉舒张所必需的。虽然THAL不重吸收水，但它们的基底膜是透水的。我们的初步数据表明，这部分是由于AQP-1，这也是在直血管表达。我们推测AQP-1将NO从塔尔转运到直小血管周细胞。首先，我们将调查是否AQP-1运输NO出的塔尔通过测量NO流出从单个，微灌注THAL分离野生型和AQP-1敲除（-/-）小鼠使用NO选择性电极。其次，我们将调查是否AQP-1运输NO进入直小血管周细胞通过测量NO流入单个，微灌注直小血管分离野生型和AQP-1 -/-小鼠使用荧光染料和荧光共聚焦显微镜。第三，我们将研究是否AQP-1依赖的NO运输参与之间的小管血管串扰的塔尔和直小血管周细胞通过测量的效果，刺激NO的生产由塔尔对NO流入下行直小血管从野生型和AQP-1 -/-小鼠使用一个单一的，孤立的塔尔与相邻的下行直小血管连接。最后，我们将测量通过基因转移技术恢复AQP-1表达的效果，特别是在塔尔、直血管周细胞或两者中：1。NO流出塔尔，2. NO流入直血管和3）THAL衍生的直血管的NO依赖性舒张。从这个建议的数据将有助于我们了解肾血流的调节。AQP-1依赖的NO从塔尔向DVR转运的缺陷可能在高血压的发展中起作用。这一提议的结果可能为开发治疗高血压的药理学工具提供新的靶点。

DESCRIPTION (provided by applicant): Hypertension afflicts approximately 1/3 of the U.S. population. The kidney plays an important role in the regulation of blood pressure through the regulation of extracellular volume. Renal nitric oxide (NO) plays an important role in the regulation of extracellular volume and thus blood pressure. Inhibition of renal NO production in general and in the renal medulla specifically causes hypertension. The latter is due to changes in medullary blood flow and nephron transport. In the renal medulla, NO dilates the vasa recta pericytes to increase medullary blood flow. At least some of this NO comes from the adjacent thick ascending limb of the loop of Henle (THAL). Free diffusion is assumed to be the primary mechanism whereby NO leaves the THAL and enters the pericyte. However we have recently shown that aquaporin-1 (AQP-1) transports NO across cell membranes 4 times faster than free diffusion and that AQP-1-dependent NO transport is required for endothelium-induced relaxation of thoracic aortas. Although THALs reabsorb no water, their basolateral membranes are water permeable. Our preliminary data show that this is in part due to AQP-1, which is also expressed in the vasa recta. We hypothesize that AQP-1 transports NO out of the THAL and into the vasa recta pericytes. First, we will investigate whether AQP-1 transports NO out of the THAL by measuring NO efflux from single, microperfused THALs isolated from wild-type and AQP-1 knockout (-/-) mice using a NO-selective electrode. Second, we will investigate whether AQP-1 transports NO into vasa recta pericytes by measuring NO influx into single, microperfused vasa recta isolated from wild-type and AQP-1 -/- mice using fluorescent dye and fluorescent confocal microscopy. Third, we will investigate whether AQP-1-dependent NO transport is involved in tubular vascular crosstalk between the THAL and vasa recta pericytes by measuring the effect of stimulating NO production by the THAL on NO influx into descending vasa recta from wild-type and AQP-1 -/- mice using a single, isolated THAL with an adjacent descending vasa recta attached. Finally, we will measure the effect of restoring AQP-1 expression by gene transfer technology specifically in the THAL, vasa recta pericytes, or both on: 1. Efflux of NO out of the THAL, 2. Influx of NO into the Vasa recta and 3) THAL-derived NO-dependent relaxation of vasa recta. Data from this proposal will contribute to our understanding of regulation of renal blood flow. Defects in AQP-1 - dependent NO transport from the THAL to the DVR may play a role in the development of hypertension. Results from this proposal may offer new targets for the development of pharmacological tools for the treatment of hypertension.