The Dynamics of Nitric Oxide in the Vascular System

描述（由申请人提供）：虽然内皮衍生放松因子（EDRF）通常被认为是一氧化氮（包括诺贝尔委员会，1998年），但关于EDRF的确切分子身份，特别是它是游离NO还是相关的氮氧化物物种，存在很多不确定性。这种不确定性的大部分原因是由于人们普遍认为游离NO的动力学不适合其作为EDRF的作用，特别是它太短暂。在本提案中，我们将专门研究这一重要问题，即，我们将确定和量化决定血管系统中NO动力学的过程。我们的三个特定目的是根据涉及的三个腔室来组织的：血管管腔、血管壁、血管腔。在具体目标1中，我们将讨论NO在管腔中的动力学。具体来说，我们假设在这个区室中定义NO动力学的主要过程是红细胞内氧合血红蛋白对NO的不可逆消耗。尽管这代表了体内NO的主要吸收，但这一过程足够缓慢，游离NO仍然可以发挥EDRF的作用；我们将描述这种迟滞的起源，这是由于红细胞内的氧合血红蛋白的封装。我们还将研究亚硝基硫醇-血红蛋白作为NO的可能载体形成的动力学能力。在特异性目的II中，我们将测试它是否是游离NO，这是血管壁血管松弛的直接效应。我们将通过测试假设来解决这个问题，如果它是游离NO，它是内皮细胞和平滑肌细胞之间的信使，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，并测试除了引起血管舒张外，NO的第二个作用是否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.