AT1 Receptors in Renal Microvascular Physiology

说明(申请人提供)：血管紧张素(Ang)II对肾脏有很强的作用，主要通过AT1受体介导。在啮齿动物中有两种独特的AT1受体亚型，AT1A和AT1B，用药理拮抗剂无法区分。因此，该项目的长期目标是确定AT1A和AT1B受体在介导Angli对肾微血管功能的作用中的作用。需要检验的总体假设是，AT1A和AT1B受体在肾微血管中的分布并不均匀；传入小动脉既有AT1A型，也有AT1B型，而出肾小动脉只有AT1A型受体。因此，AT1a和AT1B受体的代偿功能仅限于肾小球前血管系统。这一假说将在以下特定目标下得到验证：1)绘制ATIA和ATIB受体在肾小球前和后血管系统的分布；2)阐明由传入和传出小动脉AT1A和AT1B受体激活而引发的钙信号机制；3)确定微血管AT1A和AT1B受体表达和功能的变化，以响应循环Angli水平的变化；以及4)研究肾微血管AT1受体缺失对神经元(NNOS)和内皮/或内皮型一氧化氮合酶(ENOS)来源的一氧化氮(NO)反向调节血管扩张作用的影响。AT1a和/或AT1B受体被靶向干扰的小鼠将被研究以辨别AT1受体亚型的功能。Angli反应将通过直接观察肾小球前(弓形、小叶间动脉、传入小动脉)和肾小球后(传出小动脉、直降血管)血管结构来确定，方法是使用小鼠体外灌流的延髓旁肾单位技术。AT1受体亚型微血管功能及mRNA和蛋白表达/定位的调节将在不同盐摄入量、血管紧张素转换酶抑制和血管紧张素输注介导的慢性Angil水平变化过程中确定。AT1受体与内皮型一氧化氮合酶(NNOS)和内皮型一氧化氮合酶(ENOS)产生的NO对肾微血管功能的影响将通过药理学方法进行评估。这些研究的结果将描述AT1受体在控制肾微血管血流动力学中的复杂、重叠和独特的功能。

DESCRIPTION (provided by applicant): Angiotensin (Ang) II has powerful effects on the kidney which are mediated primarily by the AT1 receptor. There are 2 unique AT1 receptor subtypes in rodents, AT1A and AT1B, which cannot be distinguished using pharmacological antagonists. Accordingly, the long term goal of this project is to determine the contribution of AT1A and AT1B receptors in mediating AnglI actions on renal microvascular function. The overall hypothesis to be tested is that the distribution of the AT1 A and AT1 B receptors along the renal microvasculature is not uniform; afferent arterioles have both AT1A and AT1 B subtypes, whereas effereni arterioles have only the AT1A receptor subtype. Therefore, the compensatory functions of the AT1A and AT1B receptors are restricted to the preglomerular vasculature. The hypothesis will be tested in the following specific aims: 1) To map the distribution of the ATIA and ATIB receptors on the pre- and postglomerular vasculature; 2) To elucidate the mechanism of calcium signaling evoked by activation of afferent and efferent arteriolar AT1A and AT1B receptors; 3) To determine the changes in microvascular AT1A and AT1B receptor expression and function in response to alterations in circulating Angli levels; and 4) To examine the functional consequences of renal microvascular AT1 receptor absence on the activity of counterregulatory vasodilatory actions of nitric oxide (NO) derived from neuronal (nNOS) and/or endothelial (eNOS) nitric oxide synthases. Mice with targeted disruption of AT1A and/or AT1B receptors will be studied to discern the functions of the AT1 receptor subtypes. Angli responses will be determined by direct visualization of preglomerular (arcuate, interlobular artery, afferent arteriole) and postglomerular (efferent arteriole, descending vasa recta) vasculature using the mouse in vitro blood perfused juxtamedullary nephron technique. Regulation of AT1 receptor subtype microvascular function and mRNA and protein expression/localization will be determined during chronically altered Angil levels mediated by varied salt intake, angiotensin converting enzyme inhibition, and Angil infusion. The interaction of AT1 receptors and NO derived from nNOS and eNOS on renal microvascular function will be evaluated by pharmacological approaches. The results of these studies will delineate the complex, overlapping, and distinct functions of AT1 receptors in controlling renal microvascular hemodvnamics.