VASOMOTOR CONTROL OF DESCENDING VASA RECTA

降血管直肠的血管舒缩控制

• 批准号: 6390257
• 负责人: THOMAS L PALLONE
• 金额: $ 25.65万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2004-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6390257
• 关键词: adenylate cyclase; angiotensin II; angiotensin receptor; calcium flux; calcium indicator; enzyme inhibitors; kidney circulation; kidney pharmacology; laboratory rat; macrophage; membrane potentials; microcirculation; nitric oxide; polymerase chain reaction; protein tyrosine kinase; protein tyrosine phosphatase; receptor expression; renal medulla; renal tubule; thromboxanes; vascular endothelium permeability; vasomotion; voltage /patch clamp; voltage gated channel

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.

描述：（改编自研究者摘要）降直血管 (DVR) 是流向肾髓质的血流所经过的阻力血管 提供。血管紧张素 II (ANGII) 似乎具有收缩血管的作用。 髓质微循环并刺激髓质NO的产生。 PI 提供 初步数据表明 ANGII 刺激 AT1 和 AT2 受体 DVR 上的亚型，ANGII 诱导的收缩是由 环加氧酶产物，并且 AT1 诱导的收缩被消除 AT2受体激活。此外，DVR 内皮细胞似乎对 仅当 AT2 受体存在时，通过增加细胞内 [Ca] 来激活 AT1 被阻止。最后，AT2 受体激活似乎使 DVR 超极化 内皮细胞，同时对邻近细胞的膜电位没有影响 周细胞。提供了以下具体目标： 目标 1-利用 RT-PCR 以及对 AT2 受体阻滞剂反应性的药理学评估 验证 DVR 中 AT2 受体的表达。目标 2-测量 ANGII 诱导的 DVR 和束间肾单位的细胞内 [Ca] 反应和 NO 生成 从肾外髓质分离的片段以及膳食盐的影响 加载这些响应。目标3-利用膜渗透环核苷酸 类似物和鸟苷酸或腺苷酸环化酶抑制剂来检验假设 AT2 阻断 DVR 内皮细胞中 AT1 介导的钙信号传导 受体激活涉及环核苷酸。细胞内的作用 磷酸化事件和酪氨酸磷酸酶或激酶活性 现象也将受到审查。目标 4-利用膜片钳和 Mn 淬火 fura2 检查 AT1 和 AT2 受体激活调节的能力 内皮钙离子流入。目标 5-检验 DVR 周细胞缺乏 L 型的假设 通过检查硝苯地平阻断能力来电压操作 Ca 通道 血管收缩、ANGII 对周细胞膜电位的影响以及 膜去极化对全钙电流的影响。额外的 实验将检验 AT1 和 AT2 刺激调节的假设 细胞内周细胞[Ca]。最后，PI 假设 ANGII 限制 OMDVR 通过血栓素生成。该假设将通过检验来检验 PGH2-TxA2 受体拮抗剂阻断 ANGII 诱导的能力 血管收缩，TxA2类似物引起血管收缩的能力，以及 ANGII 刺激孤立血管中 TxB2 产生的能力。