标题：Alveolar epithelial type I cells contain transport proteins and transport sodium, supporting an active role for type I cells in regulation of lung liquid homeostasis
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2002
卷号：99
期号：4
页码：1966-1971
DOI：10.1073/pnas.042689399
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Transport of lung liquid is essential for both normal pulmonary physiologic processes and for resolution of pathologic processes. The large internal surface area of the lung is lined by alveolar epithelial type I (TI) and type II (TII) cells; TI cells line >95% of this surface, TII cells <5%. Fluid transport is regulated by ion transport, with water movement following passively. Current concepts are that TII cells are the main sites of ion transport in the lung. TI cells have been thought to provide only passive barrier, rather than active, functions. Because TI cells line most of the internal surface area of the lung, we hypothesized that TI cells could be important in the regulation of lung liquid homeostasis. We measured both Na+ and K+ (Rb+) transport in TI cells isolated from adult rat lungs and compared the results to those of concomitant experiments with isolated TII cells. TI cells take up Na+ in an amiloride-inhibitable fashion, suggesting the presence of Na+ channels; TI cell Na+ uptake, per microgram of protein, is {approx}2.5 times that of TII cells. Rb+ uptake in TI cells was {approx}3 times that in TII cells and was inhibited by 10-4 M ouabain, the latter observation suggesting that TI cells exhibit Na+-, K+-ATPase activity. By immunocytochemical methods, TI cells contain all three subunits (, {beta
