Department of Pediatrics, University of California , San Diego, California.
Division of Biomedical Sciences, University of California , Riverside, California.
Am J Physiol Lung Cell Mol Physiol. 2019 May 1;316(5):L953-L960. doi: 10.1152/ajplung.00545.2018. Epub 2019 Mar 6.
Although small airways account for the largest fraction of the total conducting airway surfaces, the epithelial fluid and electrolyte transport in small, native airway epithelia has not been well characterized. Investigations have been limited, no doubt, by the complex tissue architecture as well as by its inaccessibility, small dimensions, and lack of applicable assays, especially in human tissues. To better understand how the critically thin layer of airway surface liquid (ASL) is maintained, we applied a "capillary"-Ussing chamber (area ≈1 mm) to measure ion transport properties of bronchioles with diameters of ~2 mm isolated from resected specimens of excised human lungs. We found that the small human airway, constitutively and concurrently, secretes and absorbs fluid as observed in porcine small airways (50). We found that the human bronchiolar epithelium is also highly anion selective and constitutively secretes bicarbonate ( ), which can be enhanced pharmacologically by cAMP as well as Ca-mediated agonists. Concurrent secretion and absorption of surface liquid along with secretion help explain how the delicate volume of the fluid lining the human small airway is physiologically buffered and maintained in a steady state that avoids desiccating or flooding the small airway with ASL.
尽管小气道占据了总传导气道表面的最大部分，但小气道上皮的上皮液和电解质转运尚未得到很好的描述。毫无疑问，这一研究受到复杂的组织架构以及其不可及性、小尺寸和缺乏适用的检测方法的限制，特别是在人体组织中。为了更好地理解临界薄的气道表面液（ASL）是如何维持的，我们应用“毛细管”-Ussing 室（面积≈1 平方毫米）来测量从切除的人肺标本中分离的直径约为 2 毫米的细支气管的离子转运特性。我们发现，小的人气道与猪的小气道一样，持续并同时分泌和吸收液体（50）。我们发现，人支气管上皮细胞也是高度阴离子选择性的，并持续分泌碳酸氢盐（ ），这种分泌可以通过 cAMP 以及 Ca 介导的激动剂增强。表面液体的同时分泌和吸收以及 的分泌有助于解释为什么人体小气道的液体衬里的精细体积在生理上得到缓冲，并保持在一个避免小气道干燥或被 ASL 淹没的稳定状态。
