Molecular Mechanisms of Lymphatic Muscle Contraction

描述(申请人提供)：淋巴管通常在净静水压力和蛋白质梯度下输送液体和蛋白质。淋巴通过内在和外在淋巴泵和带瓣血管的参与而移动。淋巴管使用阶段性收缩和外在压缩来产生血流，而紧张性收缩改变阻力。在正常情况下，这种固有的泵在许多淋巴管内淋巴流的产生中起着首要的作用。与平滑肌相比，淋巴肌表现出强烈的收缩/时相收缩、更高的收缩速度和不同的细胞内钙动力学。不幸的是，人们对导致这些特征的分子机制知之甚少。这一建议的中心假设是，调节淋巴肌收缩动力学的调节机制既包括横纹肌的特征，也包括平滑肌肉的特征。为了验证这一假说，提出了以下具体目标：1)确定淋巴肌肉收缩和调节蛋白的分布；2)确定粗丝调节通路在淋巴肌肉相和紧张性收缩中的功能作用；3)确定细丝调节通路在淋巴肌肉收缩中的功能作用。我们将使用大鼠肠系膜和胸腔导管淋巴管进行分子研究。我们将使用分离/插管的肠系膜和胸腔导管淋巴管，来研究淋巴管的收缩特性。将在胸导管环制剂(包括完整的和去皮的)中进行力和钙的测量，以确定淋巴管的钙敏感性和协同机制。我们希望在淋巴肌肉中找到一种独特的收缩机械组合。我们预测淋巴管的相性和紧张性收缩将反映这个系统中存在的收缩和调节蛋白的固有性质。这些研究将首次确定淋巴收缩行为的独特机制。淋巴管的收缩机制以前是未知的，这将极大地促进我们对淋巴管功能基础的理解。

DESCRIPTION (provided by applicant): The lymphatics normally transport fluids and proteins against net hydrostatic pressure and protein gradients. Lymph is moved through the involvement of intrinsic and extrinsic lymphatic pumps and valved vessels. Lymphatics use phasic contractions and extrinsic compressions to generate flow, while tonic contractions alter resistance. Under normal conditions this intrinsic pump has been shown to be of primary importance in the generation of lymph flow within many lymphatics. Lymphatic muscle exhibits strong/phasic contractions, much higher shortening velocities and different intracellular calcium dynamics, when compared with smooth muscles. Unfortunately little information is known about the molecular mechanisms that are responsible for these characteristics. The central hypothesis of this proposal is that the regulatory mechanisms modulating the contraction dynamics of lymphatic muscle encompass the characteristics of both striated and smooth muscle. To test this hypothesis, the following specific aims are proposed: 1) To determine the distribution of contractile and regulatory proteins in lymphatic muscle; 2) to define the functional roles of thick filament regulatory pathways in phasic and tonic lymphatic muscle contraction; and 3) to determine the functional roles of thin filament regulatory pathways in lymphatic muscle contraction. We will use rat mesenteric and thoracic duct lymphatic vessels for the molecular studies. We will use isolated/cannulated vessels from mesenteric and thoracic duct lymphatics, to study the contractile characteristics of lymphatics. Force and calcium measurements will be conducted in the thoracic duct ring preparations (both intact and skinned) to determine the calcium sensitivity and cooperativity mechanisms of lymphatics. We expect to find a unique combination of contractile machinery in the lymphatic muscle. We predict that the phasic and tonic contractions of lymphatic vessels will reflect the inherent nature of the contractile and regulatory proteins that exist in this system. These studies will provide some of the first determinations of the unique mechanisms underlying lymphatic contractile behavior. The contractile mechanisms of lymphatics have not been known before and will significantly advance our understanding of the basis for the lymphatic vessel function.