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：（改编自调查员的摘要）下降的Vasa Recta （DVR）是阻力容器，流向肾脏髓质的血液为 提供。血管紧张素II（ANGII）似乎具有滋补作用以收缩 髓质微循环并刺激髓质NO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A介导的 环氧酶产物，AT1诱导的收缩被废除 AT2受体激活。此外，DVR内皮似乎对 仅在AT2受体为时，通过增加细胞内[CA]来激活AT1 阻止。最后，AT2受体激活似乎超极化DVR 内皮，虽然对相邻的膜潜力没有影响 周细胞。提供了以下特定目的：AIM 1-限制两个RT-PCR 以及对AT2受体阻滞剂的反应性的药理评估 验证DVR中AT2受体的表达。 AIM 2测量Angii引起的 细胞内[CA]反应，并且没有DVR和Interbundle Nephron的产生 从肾外髓分离出的片段和饮食盐的作用 加载这些响应。 AIM 3限制膜渗透环状核苷酸 类似物和鸟烯基或腺苷酸环化酶抑制剂以检验假设 AT2的DVR内皮中AT1介导的钙信号传导的封锁 受体激活涉及环状核苷酸。细胞内的作用 在此中，磷酸化事件和酪氨酸磷酸酶或激酶活性 现象也将被检查。瞄准4点贴片夹和Mn Quench Fura2检查AT1和AT2受体激活调节的能力 内皮CA涌入。目标5测试DVR周细胞缺乏L型的假设 电压通过检查硝苯地平阻止的能力来操作CA通道 血管收缩，Angii对周细胞膜电位的影响，以及 膜去极化对整个呼叫电流的影响。额外的 实验将测试AT1和AT2刺激调节的假设 细胞细胞内[CA]。最后，PI假设Angii收缩了 OMDVR通过血栓烷生成。该假设将通过检查 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。