Role of Lung Microvascular Vasoactivity in Control of Lung Capillary Perfusion

描述(由申请人提供)： 肺微血管之间的血流分布被认为主要受微动脉收缩和扩张的控制。然而，这种活性对微血管灌注性的影响尚不清楚。此外，大量的解剖学证据表明，肺微血管内的主动灌流控制是可能的，尽管这一课题从未被研究过。我们将使用我们开发的方法来解决我们对肺微血管控制的理解中的这些缺陷。我们将确定直接作用于肺微血管的血管活性物质，而不是作用于肺小动脉或小静脉的血管活性物质。我们还将确定这些制剂如何影响红细胞微血管的灌注性。我们将在正常肺和低氧肺以及败血症患者中进行这些研究，以确定这一对照的临床相关性。我们提出的具体目标如下：1.肺微血管对产生全肺血管收缩的药物的血管活性反应。我们将使用血管紧张素-II、缓激肽、5-羟色胺、血栓素类似物U46619或缺氧来收缩肺。在血管收缩期间，特定直径(1、2、3或4�m)的乳胶颗粒将被注入每个肺，然后肺将被迅速冷冻。微血管内的颗粒密度将在共聚焦组织学图像中测量每个直径的颗粒(每个肺一个直径)。这些直径特定的颗粒密度将被用来量化每个治疗组肺内微血管的平均直径。产生与匹配血流对照相似的微血管直径的血管收缩药将被认为主要影响小动脉。血管收缩药产生的微血管直径小于匹配血流对照中的那些，将被认为主要影响微血管。产生比匹配血流对照的微血管直径更大的血管收缩药将被认为主要影响小静脉。这些结果将使我们能够确定每种药物发挥主要血管收缩作用的血管段：小动脉、微血管或小静脉。我们会 此外，还研究了低氧对正常肺和低氧肺的影响，以及Rho激酶和一氧化氮合酶(NOS)的影响，以进一步阐明每个血管段的药理活性。这一目的的研究为AIMS 2和3.2提供了基线数据。2.肺微血管红细胞对产生全肺血管收缩的药物的灌流反应。这一目标的研究量化了在目标1中使用的条件下红细胞通过微血管的能力。该目标的目的是确定目标1中确定的微血管直径的临床相关性。我们的目标是了解目标1中确定的微血管直径的变化是否转化为红细胞灌注性的相应变化。3.肺微血管对已知可在败血症所致肺损伤中产生全肺血管收缩作用的药物的血管活性反应。这一目标的目的是了解临床相关的肺损伤如何影响肺微血管直径和反应性。已知脓毒症明显干扰肺毛细血管的血流分布，并导致呼吸/血流异常。然而，脓毒症引起的微血管直径和血管反应性的改变也可能与此有关。这是一个一无所知的问题，我们的研究将首次解决这个问题。我们将使用AIMS 1和2中使用的乳胶颗粒和红细胞方法来确定脓毒症(脂多糖输注)对微血管直径和红细胞灌注量的影响，并确定脓毒症如何改变每个血管段的药理反应性。我们的研究结果将扩大我们对正常肺和损伤肺的肺微血管血流调节的基本了解，并导致新的治疗方法，改善肺损伤的肺毛细血管灌流。

DESCRIPTION (provided by applicant): Perfusion distribution among lung microvessels is thought to be controlled mainly by arteriolar constriction and dilation. However, effects of this activity on microvessel perfusability are unknown. Furthermore, considerable anatomic evidence suggests that active perfusion control is possible within the lung microvessels themselves, although this subject has never been studied. We will address these deficits in our understanding of pulmonary microvascular control using methods we developed. We will identify vasoactive agents that act directly on pulmonary microvessels versus those that act on pulmonary arterioles or venules. We will also determine how these agents affect red cell microvessel perfusability. We will conduct these studies in normal and hypoxic lungs, and in those injured by sepsis to determine the clinical relevance of this control. We propose the following specific aims: 1. Vasoactive response of lung microvessels to pharmacologic agents that produce whole-lung vasoconstriction. We will vasoconstrict lungs using angiotensin-II, bradykinin, serotonin, the thromboxane analog U46619, or hypoxia. Latex particles of a specific diameter (1.0, 2.0, 3.0, or 4.0 �m) will be infused into each lung during vasoconstriction and the lungs will then be rapidly frozen. Particle densities within the microvessels will be measured in confocal histological images for particles of each diameter (one diameter per lung). These diameter-specific particle densities will be used to quantify the average microvessel diameter in lungs of each treatment group. Vasoconstrictors that produce microvessel diameters similar to those in matched-flow controls will be assumed to affect mainly arterioles. Vasoconstrictors that produce microvessel diameters smaller than those in matched-flow controls will be assumed to affect mainly microvessels. Vasoconstrictors that produce microvessel diameters larger than those in matched-flow controls will be assumed to affect mainly venules. These results will allow us to identify the vascular segment in which each agent exerts the majority of its vasoconstriction: in arterioles, microvessels, or venules. We will also examine the effects of hypoxia, and the effects of Rho kinase and nitric oxide synthase (NOS), in normal and hypoxic lungs to further clarify the pharmacologic reactivity of each vascular segment. The studies in this aim provide the baseline data for aims 2 and 3. 2. Pulmonary microvessel red cell perfusability response to pharmacologic agents that produce whole-lung vasoconstriction. The studies in this Aim quantify the ability of red blood cells to flo through microvessels under the conditions utilized in Aim 1. The goals of this Aim are to determine the clinical relevance of the microvessel diameters identified in Aim 1. Our objective is to learn if the changes in microvessel diameters identified in Aim 1 translate to corresponding changes in the red cell perfusability. 3. Vasoactive response of lung microvessels to pharmacologic agents known to produce whole-lung vasoconstriction in lungs injured by sepsis. The goals of this aim are to learn how lung microvessel diameters and reactivity are affected by clinically relevant lung injury. Perfusion distribution among lung capillaries is known to be markedly disturbed by sepsis, and to cause ventilation/perfusion abnormalities. However, sepsis- induced changes in microvessel diameters and vasoreactivity may be responsible for this as well. This is a subject about which nothing is known, and our studies will address it for the first time. We will use the latex particle and red cell methods employed in Aims 1 and 2 to determine how microvessel diameters and red cell perfusion are affected by sepsis (LPS infusion), and to also determine how the pharmacologic responsiveness of each vessel segment is altered by sepsis. Results of our studies will expand our basic understanding of pulmonary microvascular flow regulation in normal and injured lungs, and lead to new treatments that improve lung capillary perfusion in lung injury.