Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
Pflugers Arch. 2019 Apr;471(4):519-532. doi: 10.1007/s00424-018-2232-y. Epub 2018 Nov 5.
The lung is the interface between air and blood where the exchange of oxygen and carbon dioxide occurs. The surface liquid that is directly exposed to the gaseous compartment covers both conducting airways and respiratory zone and forms the air-liquid interface. The barrier that separates this lining fluid of the airways and alveoli from the extracellular compartment is the pulmonary epithelium. The volume of the lining fluid must be kept in a range that guarantees an appropriate gas exchange and other functions, such as mucociliary clearance. It is generally accepted that this is maintained by balancing resorptive and secretory fluid transport across the pulmonary epithelium. Whereas osmosis is considered as the exclusive principle of fluid transport in the airways, filtration may contribute to alveolar fluid accumulation under pathologic conditions. Aquaporins (AQP) facilitate water flux across cell membranes, and as such, they provide a transcellular route for water transport across epithelia. However, their contribution to near-isosmolar fluid conditions in the lung still remains elusive. Herein, we discuss the role of AQPs in the lung with regard to fluid homeostasis across the respiratory epithelium.
肺是空气和血液之间的界面，在这里发生氧气和二氧化碳的交换。直接暴露于气体腔室的表面液体覆盖着传导气道和呼吸区，并形成气液界面。将气道和肺泡的衬里液与细胞外隔室分开的屏障是肺上皮。衬里液的体积必须保持在一定范围内，以保证适当的气体交换和其他功能，如黏液纤毛清除。一般认为，这是通过平衡肺上皮的吸收性和分泌性液体转运来维持的。虽然渗透被认为是气道中液体转运的唯一原理，但在病理条件下，过滤可能有助于肺泡液的积聚。水通道蛋白（AQP）促进跨细胞膜的水通量，因此，它们为跨上皮细胞的水转运提供了细胞内途径。然而，它们对肺中近等渗流体条件的贡献仍然难以捉摸。本文讨论了 AQP 在肺中的作用，以及它们在呼吸上皮细胞的液体动态平衡中的作用。
