Physiological Basis of Vascular Contractility

描述(由申请人提供)： 流体动力是动脉、静脉和淋巴管收缩功能的重要内在调节因素。所有三种血管类型对跨壁压力和管腔切应力的变化都有反应，但它们的反应明显不同。作为对压力升高的反应，小动脉表现出强烈的、持续的收缩；小静脉表现为一过性的、弱的收缩；淋巴管增加了它们的相位收缩的速率，但张力变化很小或没有变化。剪切应力抑制了所有三个容器的压力诱导反应。此外，每种血管类型的收缩反应在身体的不同区域都是不同的，根据主要的体位静水梯度。这一假设的中心假设是血管跨壁压力的血管间和区域间差异显著地影响着平滑肌收缩蛋白表达和功能的异质性。为了验证这一假设，我们将确定血管功能、机械性能和蛋白质表达的异质性在多大程度上受跨壁压力的影响。每个目标都将利用来自4个不同区域环境(腿、颈、胸、腹部)的相邻小动脉、小静脉和淋巴管，在这些区域环境中，血管跨壁压力梯度不同。方法包括使用压力/流量可控的隔离/空管血管、力反馈控制下的线状肌图上的血管节段、mRNA、蛋白质和肌球蛋白ATPase分析、免疫荧光共聚焦显微镜。在每种血管类型中，在每个位置，我们的目的是比较：1)相对于血管壁的被动机械特性的压力和剪应力的功能性收缩反应；2)血管SM的主动长度-张力和力-速度关系；3)SM收缩和调节蛋白亚型的表达与肌球蛋白ATPase活性的关系。这些结果将综合起来，以获得这些血管中血管SM之间的相似和不同之处的更完整的图景。我们预测血管内和区域间血管力学和功能的差异将反映SM收缩蛋白亚型表达的潜在差异。此外，还预测了小动脉、小静脉和淋巴管的功能行为，以反映它们各自跨壁压力梯度的大小。这些比较以前从未进行过，这将极大地促进我们对血管收缩功能异质性的基础的理解。

DESCRIPTION (provided by applicant): Hydrodynamic forces are important intrinsic regulators of contractile function for arterial, venous and lymphatic vessels. All 3 vessel types react to changes in transmural pressure and luminal shear stress, but their responses differ dramatically. In response to pressure elevation, arterioles exhibit strong, sustained constrictions; venules transient, weak constrictions; lymphatics increase their rate of phasic contractions, with little or no change in tone. Shear stress inhibits the pressure-induced responses of all three vessels. Additionally, the contractile responses for each vessel type are variable across different regions of the body, according to the prevailing postural hydrostatic gradients. The central hypothesis of this proposal is that inter-vessel and inter-regional differences in vascular transmural pressure significantly influence the heterogeneity of smooth muscle (SM) contractile protein expression and function. To test this hypothesis, we will determine the extent to which the heterogeneity of vessel function, mechanical properties, and protein expression are determined by transmural pressure. Each aim will utilize adjacent arterioles, venules and lymphatics isolated from 4 different regional environments (leg, neck, thorax, abdomen) of the rat in which the vascular transmural pressure gradients vary. Methods include using isolated/cannulated vessels with controlled pressure/flow, vessel segments on wire myographs under force-feedback control, mRNA, protein and myosin ATPase analyses, immunofluorescence confocal microscopy. In each vessel type at each location our aims are to compare: 1) the functional contractile responses to pressure and shear stress relative to the passive mechanical properties of the vessel wall; 2) active length-tension and force-velocity relationships of vascular SM; 3) expression of SM contractile and regulatory protein isoforms relative to myosin ATPase activity. The results will be integrated to obtain a more complete picture of the similarities and differences between vascular SM in these vessels. We predict that inter-vessel and inter-regional differences in vascular mechanics and function will reflect underlying differences in the expression of SM contractile protein isoforms. In addition, the functional behaviors of arterioles, venules and lymphatics are predicted to reflect the magnitudes of their respective transmural pressure gradients. These comparisons have not been made before and will significantly advance our understanding of the basis for the heterogeneity in vascular contractile function.