REGULATION OF ACID/BASE TRANSPORT IN ALVEOLAR EPITHELIUM

肺泡上皮细胞(AEC)覆盖在肺泡表面， 这是哺乳动物的主要排酸器官。因为这些细胞 受制于相对于pCO2的不稳定的细胞外环境， 肺泡上皮细胞内pH(Phi)的调节 具有特殊的意义。在以前的工作中，已经确定 肺泡细胞phi受多种离子转运机制的调节 其能够实现酸/碱从电池中进入或挤出。 这些离子传输机制是不对称的质膜蛋白。 分布在极化的上皮细胞表面，从而使 酸/碱等效物的跨皮转运是可能的。他们的 膜极性在肺泡上的分布 上皮细胞，其根尖衬里液体的pH值是酸性的(6.9)，没有 之前已经建立了。我们将研究其中的机制 AEC的酸/碱运输是通过研究三个假设来调节的：(1) AEC的酸/碱转运是通过特定的离子转运机制进行的 相对于膜的极性具有特征分布的 它们代表了特定的运输活动 蛋白质异构体。(2)这些离子传输机制既尖锐又复杂。 在AEC中可长期调节的活性、表达和 通过特定的细胞外刺激来调节极性 在正常情况下和在疾病状态下的酸/碱运输。(3) 血管内皮细胞酸/碱转运机制的调控与定位 影响肺泡液pH值。在此提出的研究的目标 因此进一步描述了酸/碱的传输机制 在反腐败委员会，特别是研究对其活动的调节， 特定外源性因素的表达和极性与肺损伤。我们 将使用在组织上培养的大鼠肺泡上皮细胞单层 培养处理的聚碳酸酯过滤器，用于许多此类研究。这 模型特别适用于肺泡上皮细胞的研究 极性和酸/碱运输。我们将使用以下工具验证我们的发现 大鼠肺泡上皮细胞的原位研究。这样做的长期目标是 项目的目的是定义酸碱运输的重要性 肺泡上皮细胞的细胞内稳态，并证明 肺泡上皮细胞的酸/碱转运在调节中的作用 细胞外的肺泡环境。

Alveolar epithelial cells (AEC) cover the alveolar surface of the lung, which is the major acid-excreting organ in mammals. Because these cells are subject to an inconstant extracellular milieu with respect to pCO2, the regulation of intracellular pH (pHi) in alveolar epithelial cells is of particular significance. In previous work it has been established that alveolar pneumocyte pHi is regulated by several ion transport mechanisms that are capable of effecting acid/base entry or extrusion from the cell. These ion transport mechanisms are plasma membrane proteins asymmetrically distributed across polarized epithelial cell surfaces, thereby making transepithelial transport of acid/base equivalents possible. Their distribution with respect to membrane polarity across the alveolar epithelium, whose apical lining fluid pH is acidic (6.9), has not previously been established. We will investigate the mechanisms whereby acid/base transport by AEC is regulated by studying three hypotheses: (1) Acid/base transport by AEC occurs via specific ion transport mechanisms having a characteristic distribution with respect to membrane polarity across the cells, and which represent the activity of specific transport protein isoforms. (2) These ion transport mechanisms are both acutely and chronically regulable in AEC with respect to activity, expression, and polarity by specific extracellular stimuli that can thereby modulate acid/base transport under normal conditions and in disease states. (3) Regulation and localization of acid/base transport mechanisms in AEC influence alveolar fluid pH. The objectives of the studies proposed herein are therefore to further characterize the acid/base transport mechanisms in AEC, and in particular, to study regulation of their activity, expression, and polarity by specific exogenous factors and lung injury. We will use rat alveolar epithelial cell monolayers cultured on tissue culture-treated polycarbonate filters for many of these studies. This model is especially well suited for studies on alveolar epithelial polarity and acid/base transport. We will validate our findings using in situ studies on rat alveolar epithelium. The long term goals of this project are to define the importance of acid/base transport in intracellular homeostasis of alveolar epithelial cells, and to demonstrate the role of acid/base transport by alveolar epithelial cells in modulation of the extracellular alveolar milieu.