The Dynamics of Nitric Oxide in the Vascular System

描述(申请人提供)：尽管内皮衍生的松弛因子(EDRF)被公认为一氧化氮(包括诺贝尔委员会，1998)，但对于EDRF的确切分子同一性，特别是它是游离的NO还是相关的氮氧化物物种，仍有许多不确定性。这种不确定性的原因很大程度上是因为人们普遍认为，自由NO的动态不适合其作为EDRF的作用，具体地说，它太短暂了。在这项提案中，我们将具体研究这一重要问题，即我们将识别和量化决定血管系统中NO动态变化的过程。我们的三个具体目标是根据所涉及的三个部分来组织的：血管管腔、血管壁、血管腔。在特定的目标I中，我们将讨论管腔内NO的动态变化。具体地说，我们假设，在这个隔室中定义NO动力学的主要过程是红细胞内氧合血红蛋白不可逆转地消耗NO。尽管这代表了体内NO的主要吸收，但这个过程足够慢，以至于游离NO仍然可以作为EDRF发挥作用；我们将描述这种延迟的来源，这是由于红细胞内包裹了氧合血红蛋白。我们还将研究亚硝硫醇-血红蛋白作为NO的可能载体的形成的动力学能力。在特定的目的II中，我们将测试它是否是游离的NO，它是血管壁血管松弛的直接效应物。我们将通过检验这样一个假设来解决这个问题：如果内皮细胞和平滑肌细胞之间的信使NO是游离的，那么在各种条件下的松弛应该与游离NO的浓度直接相关(我们将使用NO特异性电极直接测量)。在具体目标III中，我们将讨论NO在血管周围区域的寿命，并测试NO除了导致血管扩张外，是否还有第二个作用是延长氧气从血管扩散的距离。

DESCRIPTION (provided by applicant): Although the endothelium-derived relaxing factor (EDRF) is generally acknowledged to be nitric oxide (including the Nobel committee, 1998), there is much uncertainty regarding the exact molecular identity of EDRF, specifically, whether it is free NO or a related nitrogen oxide species. Much of the reason for this uncertainty is due to the general perception that the dynamics of free NO are not suitable for its role as EDRF, specifically, that it is too short-lived. In this proposal, we will specifically examine this important issue, namely, we will identify and quantify the processes which determine the dynamics of NO in the vascular system. Our three Specific Aims are organized according to the three compartments involved: the vascular lumen, wall, ablumen. In Specific Aim I we will address the dynamics of NO in the lumen. Specifically, we hypothesize that the major process which defines NO dynamics in this compartment is the irreversible consumption of NO by oxyhemoglobin within the erythrocyte. Even though this represents the major sink for NO in vivo, this process is slow enough that free NO can still function as EDRF; we will delineate the origin for this retardation, which is due to encapsulation of oxyhemoglobin within the erythrocyte. We will also examine the kinetic competence of the formation of nitrosothiol-hemoglobin as a possible carrier of NO. In Specific Aim II we will test whether it is free NO which is the direct effector of vascular relaxation in the vessel wall. We will address this by testing the hypothesis that if it is free NO which is the messenger between the endothelial cell and the smooth muscle cell, then relaxation under a variety of conditions should directly correlate with the concentration of free NO (which we will measure directly with NO-specific electrodes). In Specific Aim III we will address the lifetime of NO in the perivascular region surrounding a vessel, and test whether in addition to causing vasodilation a second role for NO is to extend the distance that oxygen diffuses away from the vessel.