AT1 Receptors in Renal Microvascular Physiology

描述（由申请人提供）：血管紧张素（Ang）II对肾脏具有强大的作用，主要由AT 1受体介导。 啮齿类动物中有2种独特的AT 1受体亚型，AT 1A和AT 1B，无法使用药理学拮抗剂区分。 因此，本项目的长期目标是确定AT 1A和AT 1B受体在介导AnglI对肾微血管功能的作用中的贡献。 待检验的总体假设是AT 1 A和AT 1 B受体沿着肾微血管的分布不均匀;传入小动脉具有AT 1 A和AT 1 B亚型，而传出小动脉仅具有AT 1 A受体亚型。 因此，AT 1A和AT 1B受体的补偿功能仅限于肾小球前血管系统。 本研究的主要目的是：1）定位ATIA和ATIB受体在肾小球前、后血管的分布，2）阐明AT 1A和AT 1B受体激活小动脉传入和传出引起的钙信号转导机制，3）研究AT 1A和AT 1B受体在肾小球前、后血管中的分布，4）研究AT 1A和AT 1B受体激活小动脉传入和传出引起的钙信号转导机制。3）研究微血管AT_（1A）和AT_（1B）受体的表达和功能对循环Angli水平变化的响应;（4）检测肾微血管AT 1受体缺失对神经元型（nNOS）和/或内皮型（eNOS）一氧化氮合酶（NO）的反调节血管舒张作用的功能影响。 将研究靶向破坏AT 1A和/或AT 1B受体的小鼠，以辨别AT 1受体亚型的功能。 通过使用小鼠体外血液灌注延髓肾单位技术直接观察肾小球前（弓状动脉、小叶间动脉、传入小动脉）和肾小球后（传出小动脉、下行直血管）脉管系统来确定Angli反应。 在由不同的盐摄入、血管紧张素转化酶抑制和Angil输注介导的Angil水平慢性改变期间，将确定AT 1受体亚型微血管功能和mRNA和蛋白质表达/定位的调节。 通过药理学方法评价AT 1受体和来自nNOS和eNOS的NO对肾微血管功能的相互作用。 这些研究的结果将描绘复杂的，重叠的，和独特的功能的AT 1受体在控制肾微血管血流动力学。

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.