ALBUMIN TRANSPORT BY THE TRACHEAL EPITHELIUM

这项建议的长期目标是了解 白蛋白在气管内转运的机制和调节 上皮组织。白蛋白是呼吸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。这些措施包括 抗氧化剂和非特异性结合特性，参与脂质 和药物运输，并对 呼吸道粘液的物理性质。尽管有这些重要的影响， 通常认为，白蛋白到达和离开空域的时间 纯粹的扩散机制。然而，最近的研究表明， 呼吸道中的白蛋白含量可能受到高度监管，这 监管涉及到积极的运输机制。其中的变化 呼吸道白蛋白含量在一系列呼吸道疾病中可见 反映了这些运输过程中的异常情况。这些研究将 首先评估白蛋白和葡聚糖在浆膜到粘膜中的运动 方向(分泌)，而在相反方向(吸收) 完整的体外兔气管。一系列激动剂对血管内皮细胞生长的影响 将确定双向运输。然后，这些结果将是 与白蛋白和葡聚糖在汇合处的双向运动相比 原代培养兔气管上皮细胞的单层。这个 将使用相同的激动剂，并验证组织培养系统的有效性 为研究大分子的输运而确定。使用这个 系统中，我们将探索白蛋白转运的几种机制。这个 白蛋白转运涉及特定白蛋白受体的假说 具有内吞小泡和基于微管的细胞穿透，这可能 包括与溶酶体的融合将被测试。泡囊的作用 将通过确定与温度的依赖关系来评估运输 运输。微管网络的参与由以下因素决定 微管干扰剂诺可达唑和诺可达唑的前处理 秋水仙碱。转运机制的特殊性和是否存在 白蛋白受体将通过研究饱和动力学进行评估。 转运和上皮细胞上特异性白蛋白结合的程度 浮出水面。最后，将寻求与溶酶体的可能融合。 寻找白蛋白在柱子转运过程中的降解 层析法。

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.