Abstract：
A thin film of pulmonary surfactant lines the surface of the airways and alveoli, where it lowers the surface tension in the peripheral lungs, preventing collapse of the bronchioles and alveoli and reducing the work of breathing. It also possesses a barrier function for maintaining the blood-gas interface of the lungs and plays an important role in innate immunity. The surfactant film covers the epithelium lining both large and small airways, forming the first line of defense between toxic airborne particles/pathogens and the lungs. Furthermore, surfactant has been shown to relax airway smooth muscle (ASM) after exposure to ASM agonists, suggesting a more subtle function. Whether surfactant masks irritant sensory receptors or interacts with one of them is not known. The relaxant effect of surfactant on ASM is absent in bronchial tissues denuded of an epithelial layer. Blocking of prostanoid synthesis inhibits the relaxant function of surfactant, indicating that prostanoids might be involved. Another possibility for surfactant to be active, namely through ATP-dependent potassium channels and the cAMP-regulated epithelial chloride channels [cystic fibrosis transmembrane conductance regulators (CFTRs)], was tested but could not be confirmed. Hence, this review discusses the mechanisms of known and potential relaxant effects of pulmonary surfactant on ASM. This review summarizes what is known about the role of surfactant in smooth muscle physiology and explores the scientific questions and studies needed to fully understand how surfactant helps maintain the delicate balance between relaxant and constrictor needs.
摘要：
肺表面活性物质的薄膜排列在气道和肺泡的表面，在那里它降低了周围肺的表面张力，防止细支气管和肺泡塌陷，减少呼吸工作。它还具有维持肺血气界面的屏障功能，并在先天免疫中起重要作用。表面活性剂膜覆盖上皮内衬大和小气道，在有毒的空气传播颗粒/病原体和肺部之间形成第一道防线。此外，表面活性剂已被证明可以在暴露于气道平滑肌激动剂后放松气道平滑肌（ASM），暗示了一个更微妙的功能。表面活性剂是掩蔽刺激性感觉受体还是与其中之一相互作用是未知的。表面活性剂对气道平滑肌的松弛作用在上皮层裸露的支气管组织中不存在。前列腺素合成的阻断抑制了表面活性剂的松弛功能，表明前列腺素可能参与其中。表面活性剂具有活性的另一种可能性，即通过ATP依赖性钾通道和cAMP调节的上皮氯通道（CFTR）进行了测试，但无法证实。因此，本综述讨论了肺表面活性物质对气道平滑肌的已知和潜在的松弛作用机制。这篇综述总结了表面活性剂在平滑肌生理学中的作用，并探讨了充分了解表面活性剂如何帮助维持松弛剂和收缩剂需求之间的微妙平衡所需的科学问题和研究。
