Renal NaCl Delivery and ROS Production in mTAL

项目1假设Dahl盐敏感（SS）大鼠在喂食高盐饮食时，将在肾髓质粗升支（mTAL）中重吸收大于正常量的NaCl，这反过来将刺激活性氧（ROS）的过量产生，从而减少髓质血流量（MBF）。与盐不敏感对照SS大鼠相比，SS大鼠的mTAL表达更大量的Na/K/2CI共转运蛋白。13 并将确定它们是否还表达更大量的Na/H交换剂（NHE）亚型，这可能是导致过量超氧化物（O*2~）产生的原因。我们提出，增加的NaCl的管腔递送连同外髓间质NaCl浓度的增加可以刺激NAD（P）H氧化酶并增强O*2-和H2 O2的产生。将确定O2-和/或H2 O2的更大扩散是否发生在 在NO生物利用度降低的情况下，mTAL对直肠小血管周细胞的影响以及这是否会导致MBF减少。将使用骨髓组织条的时间分辨荧光视频显微镜对这些事件进行研究。这些观察结果的生理相关性将通过在清醒的仪器大鼠中进行的研究进行评估。骨髓间质O_2 ~-、H_2O_2、NO和骨髓间质 将使用植入的微透析纤维获得[氯化钠]。在盐（NaCl）摄入量增加和高血压发生之前和之后，每天使用植入的光纤和激光多普勒技术以及留置动脉导管测量这些清醒大鼠的髓质血流和动脉压变化。该项目有三个具体目标：1）确定是否暴露于 与对照SS.13BN大鼠相比，通过小管微灌注和/或浴灌流增加NaCl的mTAL导致SS中更大的mTAL产生O*2-或H2 O2，以及随后的周围直小血管的收缩; 2）探索细胞机制，其中增加NaCl向mTAL的管腔递送和增加间质NaCl浓度增强SS大鼠中O *2-产生; 3）表征 在清醒的SS大鼠中肾髓质产生O*2-、H2 O2和NO的时间响应，以确定在增加NaCl摄入后ROS的增加是否引发髓质血流量的减少。

Project 1 hypothesizes that Dahl salt-sensitive (SS) rats when fed a high salt diet will reabsorb greater than normal amounts of NaCI in the renal medullary thick ascending limb (mTAL) that in turn will stimulate excess production of reactive oxygen species (ROS) and thereby reduce medullary blood flow (MBF). The mTAL of SS rats express greater amounts of Na/K/2CI co-transporter than salt-insensitive control SS.13 rats and it will be determined if they also express greater amounts of isoforms of the Na/H exchanger (NHE) that could account for excess superoxide (O*2~) production. We propose that increased luminal delivery of NaCI together with increases of outer medullary interstitial NaCI concentration may stimulate NAD(P)H oxidase and enhance production of O*2" and H2O2. It will be determined if greater diffusion of O'2~ and/or H2O2 occurs from mTAL to vasa recta pericytes in the presence of reduced NO bioavailability and whether this leads to a reduction of MBF. These events will be studied using time resolved fluorescence videomicroscopy of medullary tissue strips. Physiological relevance of these observations will be assessed by studies in conscious instrumented rats. Sequential measurements of medullary interstitial O'2~, H202, NO and medullary interstitial [NaCI] will be obtained using implanted microdialysis fibers. Changes of medullary blood flow and arterial pressure will be measured daily in these conscious rats using implanted optical fibers and laser-Doppler techniques together with indwelling arterial catheters before and following an increase in salt (NaCI) intake and the development of hypertension. The project is defined by three specific aims: 1) To determine if exposure of mTAL to increased NaCI by either tubular microperfusion and/or bath superfusion results in greater mTAL production of O*2" or H2O2 and subsequent constriction of surrounding vasa recta vessels in SS compared to the control SS.13BN rats; 2) To explore the cellular mechanisms whereby increased luminal delivery of NaCI to mTAL and increases of interstitial NaCI concentrations enhance 0*2" production in SS rats; 3) To characterize the temporal responses of renal medullary production of O*2", H2O2, and NO in conscious SS rats to determine if increases in ROS initiate reductions of medullary blood flow following increased NaCI intake.