ALBUMIN TRANSPORT BY THE TRACHEAL EPITHELIUM

本提案的长期目标是了解 白蛋白经气管转运的机制和调节 上皮 白蛋白是气道衬里的主要蛋白质成分 流体，具有许多重要的性质和功能。 这些包括 抗氧化和非特异性结合特性，参与脂质 和药物转运，并对 气道粘液的物理性质。 尽管有这些重要的影响， 通常认为，白蛋白通过以下方式到达和离开空气空间： 纯粹的扩散机制。 然而，最近的研究表明， 气道中的白蛋白含量可能受到高度调节， 调节涉及主动运输机制。 中的改变的 在广泛的气道疾病中观察到的气道白蛋白含量可能 反映了这些运输过程中的异常。 这些研究将 首先评估白蛋白和葡聚糖在浆膜到粘膜中的移动 方向（分泌），并在相反的方向（吸收），在 完整的体外兔气管。 一系列激动剂对 将确定双向传输。 这些结果将是 与白蛋白和葡聚糖在融合细胞中的双向移动相比， 原代培养的兔气管上皮细胞单层。 的 将使用相同的激动剂，并且组织培养系统的有效性 为研究大分子的输运确定。 使用此 系统，将探讨白蛋白转运的几种机制。 的 白蛋白转运涉及特异性白蛋白受体假说 具有内吞囊泡和基于微管的转胞吞作用， 包括与溶酶体融合。 Vesicular的作用 运输将通过确定温度依赖性进行评估， 运输 微管网络的参与决定于 用微管破坏剂诺考达唑预处理， 秋水仙碱 转运机制的特异性和 将通过研究饱和动力学来评估白蛋白受体 运输的能力和特异性白蛋白结合上皮细胞的程度 面 最后，将通过以下方法寻求与溶酶体的可能融合： 寻找在用柱运输期间白蛋白的降解 层析

The long term objectives of this proposal are to understand the mechanisms and regulation of albumin transport across the tracheal epithelium. Albumin is a major protein constituent of the airways lining fluid and has many important properties and functions. These include anti-oxidant and non-specific binding properties, participation in lipid and drug transport, and having profound reversible effects on the physical properties of airway mucus. Despite these important effects, it is generally held that albumin reaches, and leaves the airspaces by purely diffusive mechanisms. Recent studies however, suggest that albumin content in the airways may be highly regulated, and that this regulation involves active transport mechanisms. the alterations in airways albumin content seen in a wide range of airways diseases may reflect abnormalities in these transport processes. these studies will first evaluate albumin and dextran movement in both the serosa to mucosa direction (secretion), and in the opposite direction (absorption) in the intact in-vitro rabbit trachea. The effect of a range of agonists on bidirectional transport will be determined. these results will then be compared to bidirectional albumin and dextran movement across a confluent monolayer of rabbit tracheal epithelial cells in primary culture. The same agonists will be used, and the validity of the tissue culture system for the study of macro-molecular transport determined. Using this system, several mechanisms of albumin transport will be explored. The hypothesis that albumin transport involves specific albumin receptors with endocytotic vesicles and microtubular based transcytosis which may include fusion with lysosomes will be tested. The role of vesicular transport will be assessed by determining the temperature dependence of transport. The participation of the microtubular network determined by pre-treatment with the microtubule-disrupting agents nocodazole and colchicine. The specificity of the transport mechanisms and presence of albumin receptors will be assessed by studying the saturation kinetics of transport and the degree of specific albumin binding on the epithelial surface. Lastly, possible fusion with lysosomes will be sought by looking for degradation of albumin during transport with column chromatography.