Neural Control of Sodium Balance in Hypertension: Exercise

描述（由申请人提供）：高血压困扰着许多人，是一种主要的心血管危险因素。动态运动训练降低高血压，但其机制尚不完全清楚。神经机制在调节动脉压的急性变化中起关键作用，而肾脏机制在更大程度上参与容量调节和长期压力控制。肾交感神经调节钠重吸收和肾素分泌。因此，神经和肾脏机制以整合和协调的方式发挥作用以调节动脉压。运动训练可以通过调节这一整合系统发挥其效益。我们假设，在2肾1夹高血压（2K-1C HTN），高血压大鼠模型与激活的肾素-血管紧张素-醛固酮系统和增加的交感神经活动，自愿动态运动训练将减少传出肾交感神经活动（RSNA）通过增强一氧化氮诱导的GABA能抑制室旁核（PVN）。反过来，传出RSNA的减少将通过降低远端肾单位中上皮Na通道（ENaC）的丰度和功能来增加尿Na排泄。我们有三个具体目标：（1）评价自由转轮运动是否能降低2K-1C HTN大鼠的体循环动脉压、降低传出交感神经血管紧张度和增加动脉压力反射敏感性：（2）确定自由转轮运动是否能增强PVN内的一氧化氮信号，从而增加2K-1C HTN大鼠传出RSNA的GABA能抑制和改善压力反射功能;（3）确定与随意转轮运动相关的减弱的RSNA是否会减少2K-1C HTN远端肾单位的ENaC数量，从而增加尿Na排泄，增强对生理应激（如急性Na负荷）的反应能力。我们将使用一个经典的药理学方法，以及在体内转移的显性负结构的神经元型一氧化氮合酶（nNOS）到PVN在久坐不动和运动训练的假夹和2K-1C HTN大鼠，并确定他们的血流动力学参数，RSNA和压力反射功能在清醒，不受限制的状态。我们将测量大鼠肾皮质微粒体中ENaC的丰度，并评估在正常和急性Na负荷条件下，有和没有肾脏去神经支配的久坐和运动训练大鼠的肾功能和尿Na排泄。这些研究将为心血管健康提供直接的战略药理学和非药理学干预措施，这些干预措施可以很容易地转化为临床实践。

DESCRIPTION (provided by applicant): Hypertension afflicts a great number of individuals and is a major cardiovascular risk factor. Dynamic exercise training decreases high blood pressure, but the mechanisms are incompletely understood. Neural mechanisms play a key role in regulating acute changes in arterial pressure, whereas renal mechanisms participate to a greater extent in volume regulation and long term control of pressure. Renal sympathetic nerves modulate sodium reabsorption and renin secretion. Thus, neural and renal mechanisms function in an integrated and concerted manner to regulate arterial pressure. Exercise training may exert its benefit by modulating this integrated system. We hypothesize that in 2 kidney-1 clip hypertension (2K-1C HTN), a rat model of hypertension with an activated renin-angiotensin-aldosterone system and increased sympathetic activity, voluntary dynamic exercise training will decrease efferent renal sympathetic nerve activity (RSNA) by enhancing nitric oxide-induced GABAergic inhibition within the paraventricular nucleus (PVN). In turn, the decrease in efferent RSNA will increase urinary Na excretion by decreasing the abundance and function of the epithelial Na channel (ENaC) in the distal nephron. We have 3 specific aims: (1) To assess whether voluntary wheel exercise will decrease systemic arterial pressure, decrease efferent sympathetic vasomotor tone, and increase arterial baroreflex sensitivity in 2K-1C HTN rats; (2) To ascertain whether voluntary wheel exercise will enhance nitric oxide signaling within the PVN, resulting in increased nitric oxide-induced GABAergic inhibition of efferent RSNA and improved baroreflex function in 2K-1C HTN rats; and (3) To determine whether the attenuated RSNA associated with voluntary wheel exercise will decrease the number of ENaC in the distal nephron of 2K-1C HTN, thereby increasing urinary Na excretion and enhancing the ability to respond to physiological stress such as acute Na loading. We will use a classic pharmacologic approach as well as in vivo transfer of dominant negative constructs for neuronal nitric oxide synthase (nNOS) into the PVN in sedentary and exercise trained sham-clipped and 2K-1C HTN rats and ascertain their hemodynamic parameters, RSNA and baroreflex function in the conscious, unrestrained state. We will measure the abundance of ENaC in microsomes of rat renal cortex and evaluate renal function and urinary Na excretion in sedentary and exercise trained rats with and without renal denervation under normal and acute Na loading conditions. These studies will provide data to direct strategic pharmacologic and nonpharmacologic interventions for cardiovascular health that may be readily translated into clinical practice.