Vasomotor Control of Descending Vasa Recta

描述(申请人提供)：肾髓质的微循环通过Henle环和集合管将NaCI和尿素沉积到间质中，并将血流分配到肾脏的缺氧区。大量证据表明，髓质灌注与肾脏调节盐分和水的排泄以及急性肾功能衰竭的发生有关。直肠降血管(DVR)是直径15微米的微动脉，血流通过它到达髓质。DVR周围环绕着平滑肌/周细胞，这些细胞传递收缩特性来调节血管活动。我们现在已经建立了研究DVR周细胞钙信号和通道结构的方法。利用这些方法，我们发现周细胞通过激活依赖于钙离子的CI-电导和抑制K+通道而去极化。这些事件伴随着血管紧张素II诱导的血管收缩。为了加深对DVR周细胞生理学的认识，我们提出了以下目标：1)我们将研究调控周细胞膜电位的钙依赖的CI-电导的生理特性。我们将确定阴离子的选择性和对全细胞电流和我们先前确定的11ps CICA通道抑制剂的敏感性。我们将测试蛋白激酶C和蛋白激酶A在大鼠周细胞CICA通道激活和失活中的作用。目的2)研究血管紧张素II(Ang11)对周细胞Kv通道的抑制作用。我们将测试Ang11可抑制的全细胞电流的阳离子选择性。我们将确定Ang11在细胞贴附斑块中抑制的58pS Kv通道的阳离子选择性和激活机制。目的3)研究20-HETE对血管紧张素Ⅱ诱导的DVR血管收缩和Kv通道抑制的调节作用。我们将测试20-HETE在调节周细胞膜电位和抑制K+通道中的作用。目的4)研究DVR周细胞内钙内流的途径。我们将研究钙储存耗尽开启的钙离子进入通道的电流电压特性和阳离子选择性。我们将验证电压操作的钙离子内流参与周细胞信号传导的假设。我们将确定VOCC和非选择性阳离子通道在Ang11信号转导中的作用，并测试蛋白激酶C在其激活中的作用。

DESCRIPTION (provided by applicant): The microcirculation of the renal medulla traps NaCI and urea deposited to the interstitium by the loops of Henle and collecting ducts and distributes blood flow to a hypoxic region of the kidney. Substantial evidence has linked medullary perfusion to renal regulation of salt and water excretion and genesis of acute renal failure. Descending vasa recta (DVR) are 15 um diameter arteriolar microvessels through which blood flow reaches the medulla. DVR are surrounded by smooth muscle / pericytes that impart contractile properties to regulate vasoactivity. We have now established methods to study Ca 2+ signaling and channel architecture of the DVR pericyte. Using those methods we have shown that pericytes depolarize through activation of a Ca 2+-dependent CI- conductance and inhibition of K+ channels. These events accompany angiotensin II induced vasoconstriction. To advance our understanding of the physiology of the DVR pericyte, we propose the following aims: Aim 1) We will examine the physiological properties of the Ca 2+-dependent CI- conductance that regulates pericyte membrane potential. We will determine the anion selectivity and sensitivity to inhibitors of whole cell currents and the 11 pS CICa channel we previously identified. We will test the roles of protein kinase C and protein kinase A in the activation and inactivation of the rat pericyte CICa channel. Aim 2) We will examine pericyte Kv channel suppression by angiotensin II (Angll). We will test the cation selectivity of Angll suppressible whole cell currents. We will determine the cation selectivity and activation mechanisms of a 58 pS Kv channel that Angll suppresses in cell attached patches. Aim 3) We will test the role of 20-HETE to mediate Angll induced DVR vasoconstriction and Kv channel inhibition. We will test the role of 20-HETE to regulate pericyte membrane potential and suppress K+ channels. Aim 4) We will determine which pathways participate in Ca 2+ entry in DVR pericytes. We will examine the current voltage characteristics and cation selectivity of Ca 2+ entry pathways opened by Ca 2+store depletion. We will test the hypothesis that voltage operated Ca 2+ entry participates in pericyte signaling. We will determine the role of VOCC and nonselective cation channels in Angll signaling and test a role for protein kinase C in their activation.