Cellular l-arginine uptake in hypertension

肾脏中的一氧化氮(NO)在水、电解质平衡和血压的调节中起着关键作用。NO的产生和NO依赖效应的产生都不依赖于细胞外的L精氨酸和细胞内L精氨酸的摄取，这一观点已被广泛接受；然而，我们实验室和其他实验室最近的一系列研究为质疑这一观点提供了理由。这些研究表明，直接向肾髓质补充一氧化氮合酶底物L精氨酸可预防盐敏感型高血压大鼠的钠敏感型高血压。进一步的实验表明，L精氨酸的细胞利用度可以调节肾脏中NO和ROS的产生。我们推测Dahl SS/MCW大鼠肾小管段和血管段的L-精氨酸-一氧化氮途径的缺陷通过减少NO的可获得性和/或增加ROS水平而参与了钠敏感型高血压的发生。我们将在三个具体目标上检验这一假设。目标1 将利用细胞和分子技术来量化SS/MCW大鼠整个组织以及分离的肾小管和血管与对照组大鼠对L精氨酸摄取的差异。这一目标的进一步研究将表征改变的L精氨酸摄取机制对SS/MCW大鼠肾小管和血管释放NO的影响。目的2采用新型体内微透析技术，研究L-精氨酸转运缺陷是否导致SS/MCW大鼠肾脏NO利用率降低和自由基水平升高。此外，还将确定细胞对L精氨酸摄取的增加是否会使SS/MCW大鼠的NO和ROS水平正常化。目标3的实验将确定当肾脏中的NO和ROS水平通过改变细胞对L-精氨酸的摄取而受到控制时，对肾功能和动脉血压的影响。本研究旨在探讨细胞摄取L精氨酸对SS/MCW大鼠和对照组大鼠急性血压-利钠-利尿关系、肾内血流分布、水电解质平衡和动脉血压的长期调节作用。总之，这一综合方法将确定阳离子氨基酸转运体(CAT)细胞精氨酸摄取在Dahl SS/MCW大鼠肾脏产生NO和ROS、调节肾脏钠排泄和长期控制动脉血压中的重要作用。这些研究的结果应该会为研究这一角色提供新的见解 阳离子氨基酸转运在控制肾功能和动脉血压中的作用。此外，这些结果可能揭示改变膳食氨基酸含量和/或操纵L-精氨酸摄取机制可能会降低普通人群的高血压发病率。

Nitric oxide (NO) in the kidney plays a critical role in the regulation of fluid and electrolyte balance and blood pressure. It has been widely accepted that both the production of NO and NO-dependent effects, are independent of extracellular L-arginine and cellular L-arginine uptake; yet a series of recent studies from our laboratory and other laboratories has provided reason to question this view. These studies have demonstrated that supplementation of L-arginine, the substrate for NO synthase (NOS), directly into the renal medulla prevents sodium sensitive hypertension in the Dahl salt-sensitive (SS/Mcw) rat. Further experiments indicate that the cellular availability of L-arginine can regulate the production of NO and reactive oxygen species (ROS) in the kidney. We hypothesize that a deficiency in the L-arginine-nitric oxide pathway in the tubular and vascular segments of the kidney of the Dahl SS/Mcw rat contributes to the development of sodium-sensitive hypertension by reducing the availability of NO and/or increasing the levels of ROS. We will test this hypothesis in three Specific Aims. Aim 1 will utilize cellular and molecular techniques to quantify the differences in L-arginine uptake in whole tissue and isolated renal tubules and blood vessels of the SS/Mcw rat in comparison to control rats. Further studies in this aim will characterize the influence of altered L-arginine uptake mechanisms on NO release in renal tubules and blood vessels of the SS/Mcw rat. Aim 2 will employ novel in vivo microdialysis techniques to determine if the deficiency in L-arginine transport contributes to the decreased availability of NO and elevation in free radicals observed in the kidney of the SS/Mcw rat. Moreover, it will be determined if increased cellular L-arginine uptake will normalize the levels of NO and ROS in the SS/Mcw rat. Experiments in Aim 3 will then determine the effects on renal function and arterial blood pressure when NO and ROS levels in the kidney are manipulated by altering cellular L-arginine uptake. Studies in this aim will describe the in vivo effects of manipulation of cellular L-arginine uptake on the acute pressure-natriuresis-diuresis relationship, intrarenal blood flow distribution, and the long-term regulation of fluid and electrolyte balance and arterial blood pressure in SS/Mcw and control rats. Together, this integrated approach will determine the important role of cellular arginine uptake by cationic amino acid transporters (CAT) in the production of NO and ROS in the kidney, the regulation of renal sodium excretion, and the long-term control of arterial blood pressure in the Dahl SS/Mcw rat. Results of these studies should provide novel insights into the role of cationic amino acid transport in the control of renal function and arterial blood pressure. Moreover, these results may reveal that altering the dietary amino acid content and/or manipulating L-arginine uptake mechanisms may reduce the incidence of hypertension in the general population.