VASOMOTOR CONTROL OF DESCENDING VASA RECTA

描述：(改编自《调查者摘要》)直肠血管下行 (DVR)是阻力血管，流向肾髓质的血液通过这些血管 供货。血管紧张素II(AngII)似乎有补益作用，可以收缩 促进髓质微循环，刺激髓质NO的产生。PI提供了 初步数据表明血管紧张素转换酶激活AT1和AT2受体 DVR上的亚型，血管紧张素Ⅱ诱导的收缩是由 环氧合酶产物，AT1诱导的收缩可被 AT2受体激活。此外，DVR内皮细胞似乎对 仅当AT2受体被激活时，通过增加细胞内[Ca]来激活AT1 被封锁了。最后，AT2受体的激活似乎使DVR超极化。 血管内皮细胞，而对邻近细胞膜电位无影响 周细胞。提供了以下具体目标：目标1-利用RT-PCR 以及对AT2受体阻滞剂的药理学反应评估 验证AT2受体在DVR中的表达。目的2-测量血管紧张素Ⅱ诱导 DVR和束间肾单位细胞内[Ca]反应和NO的产生 肾外髓节段的分离及食盐的影响 正在加载这些响应。目的3-利用膜透过性环核苷酸 类似物和鸟苷或腺苷环化酶抑制剂来检验这一假设 AT2阻断AT1介导的DVR内皮细胞钙信号 受体的激活涉及环核苷酸。细胞内的作用 其中的磷酸化事件和酪氨酸磷酸酶或激酶活性 我们还将研究这一现象。目的4-利用膜片钳和锰猝灭 检测AT1和AT2受体激活的调节能力 内皮细胞钙内流。目的5-检验DVR周细胞缺乏L型的假说 硝苯地平阻断电压依赖性钙通道的实验研究 血管收缩，血管紧张素Ⅱ对周细胞膜电位的影响，以及 膜去极化对整体钙电流的影响。其他内容 实验将检验AT1和AT2刺激调制的假设 周细胞内[Ca]。最后，PI假设Angii约束 通过血栓烷生成的OMDVR。这一假设将通过检查 前列环素-血栓素A_2受体拮抗剂阻断血管紧张素Ⅱ诱导的能力 血管收缩，TXA2类似物引起血管收缩的能力，以及 血管紧张素转换酶II刺激孤立血管产生TxB2的能力。

DESCRIPTION: (Adapted from the Investigator's Abstract) Descending vasa recta (DVR) are resistance vessels through which blood flow to the renal medulla is supplied. Angiotensin II (ANGII) appears to have tonic effects to constrict the medullary microcirculation and stimulate medullary NO production. The PI offers preliminary data suggesting that ANGII stimulates both AT1 and AT2 receptor subtypes on DVR, that ANGII-induced constriction is mediated by a cyclooxygenase product, and that the AT1-induced constriction is abrogated by AT2 receptor activation. Moreover, the DVR endothelium appears to respond to AT1 activation by increasing intracellular [Ca] only when AT2 receptors are blocked. Finally, AT2 receptor activation appears to hyperpolarize DVR endothelium, while having no effect on membrane potential of neighboring pericytes. The following specific aims are provided: Aim 1-Utilize both RT-PCR and a pharmacological assessment of responsiveness to AT2 receptor blockers to verify expression of the AT2 receptor in DVR. Aim 2-Measure ANGII-induced intracellular [Ca] responses and NO generation by DVR and interbundle nephron segments isolated from the renal outer medulla, and the effect of dietary salt loading on these responses. Aim 3-Utilize membrane permeant cyclic nucleotide analogues and guanylate or adenylate cyclase inhibitors to test the hypothesis that blockade of AT1-mediated calcium signaling in DVR endothelia by AT2 receptor activation involves cyclic nucleotides. The role of intracellular phosphorylation events and tyrosine phosphatase or kinase activity in this phenomenon will also be examined. Aim 4-Utilize patch clamp and Mn-quench of fura2 to examine the ability of AT1 and AT2 receptor activation to modulate endothelial Ca influx. Aim 5-Test the hypothesis that DVR pericytes lack L-type voltage operated Ca channels by examining the ability of nifedipine to block vasoconstriction, the effect of ANGII on pericyte membrane potential, and the effect of membrane depolarization on whole call Ca currents. Additional experiments will test the hypothesis that AT1 and AT2 stimulation modulates pericyte intracellular [Ca]. Finally, the PI hypothesizes that ANGII constricts OMDVR via thromboxane generation. This postulate will be tested by examining the ability of a PGH2-TxA2 receptor antagonist to block ANGII-induced vasoconstriction, the ability of a TxA2 analogue to cause vasoconstriction, and the ability of ANGII to stimulate TxB2 production in isolated vessels.