Vasomotor Control of Descending Vasa Recta

描述（由申请人提供）：肾髓质的微循环捕获NaCl和尿素以促进尿浓度，并提供代谢物以减轻缺氧。直降血管（DVR）是直径15mm的小动脉微血管，为髓质提供所有血液。DVR通过腹腔平滑肌/周细胞的收缩调节髓质灌注。我们已经建立了研究周细胞收缩、Ca2+信号和离子通道结构的方法。周细胞膜电位的去极化打开了传导Na+ (NaV)或Ca2+ (CaV)的电压门控阳离子进入通道。反过来，通过Ca2+依赖的Cl-通道（CaCC）激活和K+通道抑制的组合发生去极化。我们提供的证据表明，DVR阳离子电导受到NO和血红素加氧酶（HO）的严重调节，并且在Dahl盐敏感大鼠和eNOS无小鼠中被修饰。我们将在正常和高血压鼠模型中研究一氧化氮合酶（NOS）和HO的内在活性对DVR周细胞CaV的调节。目的1将检测一氧化氮合酶（NOS）和NO对DVR周细胞CaV的调节作用。我们将在大鼠和eNOS / nNOS缺失小鼠的DVR壁中确定哪些CaV亚类被NO抑制，哪些NOS异构体产生NO。相关的信号通路将被描述。最后，DVR NaV电导的作用将研究其在Ca2+导电“滑移模式”或与Na+/Ca2+交换相一致的操作。目的2将研究血红素加氧酶/ CO对DVR周细胞CaV的调控，测试HO的激活和抑制对CaV电导、膜电位和血管收缩的影响。我们将采用在体内上调和降低HO- 1表达的方法来测试对DVR通道活性和收缩性的影响。目的3将检查盐敏感性高血压患者周细胞电压门控Ca2+进入途径的改变。我们将确定哪种通道电导导致了Dahl/SS周细胞的去极化状态。我们将测量一氧化氮生成率，并研究提供l -精氨酸的后果，这是一种已知的逆转髓质一氧化氮生成缺乏的策略。我们将测试HO-1的上调是否会使Dahl/SS大鼠的CaV电导和膜电位正常化，并检测髓内CaV阻断对这些动物的髓质灌注增强的能力。

DESCRIPTION (provided by applicant): The microcirculation of the renal medulla traps NaCl and urea to facilitate urinary concentration and supplies metabolites to mitigate hypoxia. Descending vasa recta (DVR) are 15 mm diameter arteriolar microvessels that supply all blood flow to the medulla. Through contraction of abluminal smooth muscle / pericytes, DVR regulate medullary perfusion. We have established methods to study contraction, Ca2+ signaling and ion channel architecture of the pericytes. Depolarization of pericyte membrane potential opens voltage gated cation entry channels that conduct Na+ (NaV) or Ca2+ (CaV). In turn, depolarization occurs through a combination of Ca2+ dependent Cl- channel (CaCC) activation and K+ channel inhibition. We provide evidence that DVR cation conductance is heavily regulated by NO and heme oxygenase (HO) and that it is modified in Dahl salt sensitive rats and eNOS null mice. We will study the regulation of DVR pericyte CaV by intrinsic activity of nitric oxide synthase (NOS) and HO in normal and hypertensive rodent models. Aim 1 will test the regulation of DVR pericyte CaV by nitric oxide synthase (NOS) and NO. We will identify which CaV subclasses are suppressed by NO and which NOS isoforms generate NO in the DVR wall of rats and eNOS / nNOS null mice. The relevant signaling pathways involved will be delineated. Finally, a role for the DVR NaV conductance will be studied with respect to its operation in Ca2+ conducting "slip mode" or in concert with Na+/Ca2+ exchange. Aim 2 will study the regulation of DVR pericyte CaV by heme oxygenase / CO. We will test the ability of HO activation and suppression to modify CaV conductance, membrane potential and vessel contraction. We will employ methods to upregulate and reduce expression of HO- 1 in vivo to test the consequences on DVR channel activity and contractility. Aim 3 will examine alteration of pericyte voltage gated Ca2+ entry pathways in salt sensitive hypertension. We will determine which channel conductances account for the depolarized state of Dahl/SS pericytes. We will measure rates of NO generation and study the consequences of supplying L-arginine, a maneuver known to reverse paucity of medullary NO generation. We will test whether upregulation of HO-1 normalizes CaV conductance and membrane potential in Dahl/SS rats and examine the ability of intramedullary CaV blockade to augment perfusion of the medulla in those animals.