Role of Lung Microvascular Vasoactivity in Control of Lung Capillary Perfusion

描述（由申请人提供）： 肺微血管之间的灌注分布被认为主要受小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是未知的。此外，相当多的解剖学证据表明，主动灌注控制是可能的肺微血管本身，虽然这个问题从来没有被研究过。我们将使用我们开发的方法来解决这些缺陷，以了解肺微血管控制。我们将鉴别直接作用于肺微血管的血管活性剂和作用于肺小动脉或小静脉的血管活性剂。我们还将确定这些药物如何影响红细胞微血管灌注性。我们将在正常和缺氧的肺中进行这些研究，并在脓毒症损伤的肺中进行这些研究，以确定这种对照的临床意义。我们提出以下具体目标：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或缺氧使肺血管收缩。在血管收缩期间，将特定直径（1.0、2.0、3.0或4.0 μ m）的乳胶颗粒注入每个肺中，然后将肺迅速冷冻。将在共聚焦组织学图像中测量每种直径颗粒（每个肺一种直径）的微血管内颗粒密度。这些直径特异性颗粒密度将用于量化每个处理组肺中的平均微血管直径。血管收缩剂产生的微血管直径与匹配流量对照相似，将被认为主要影响小动脉。血管收缩剂产生的微血管直径小于匹配流量控制中的微血管直径，将被认为主要影响微血管。血管收缩剂产生的微血管直径大于匹配流量控制，将被假定为主要影响小静脉。这些结果将使我们能够确定每种药物发挥大部分血管收缩作用的血管段：小动脉、微血管或小静脉。我们将 还检查了正常和缺氧肺中缺氧的影响，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学反应性。这一目标的研究为目标2和3提供了基线数据。2.肺微血管红细胞灌注对产生全肺血管收缩的药物的反应。本目标中的研究量化了红细胞在目标1中使用的条件下流过微血管的能力。本目标旨在确定目标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.肺微血管对已知可引起脓毒症肺损伤的全肺血管收缩的药物的血管活性反应。目的是了解肺微血管直径和反应性如何受到临床相关肺损伤的影响。肺毛细血管之间的灌注分布已知被脓毒症显著干扰，并导致通气/灌注异常。然而，脓毒症引起的微血管直径和血管反应性的变化可能也是原因之一。这是一个未知的主题，我们的研究将首次解决这个问题。我们将使用目的1和2中采用的乳胶颗粒和红细胞方法来确定败血症（LPS输注）如何影响微血管直径和红细胞灌注，并确定败血症如何改变每个血管节段的药理学反应性。 我们的研究结果将扩大我们对正常和损伤肺中肺微血管流量调节的基本理解，并导致新的治疗方法，改善肺损伤中的肺毛细血管灌注。

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.