Wu D X, Lee C Y, Uyekubo S N, Choi H K, Bastacky S J, Widdicombe J H
Children's Hospital Oakland Research Institute, California 94609, USA.
Am J Physiol. 1998 Mar;274(3):L388-95. doi: 10.1152/ajplung.1998.274.3.L388.
The luminal surface of airways is lined by a thin film of airway surface liquid (ASL). Physiological regulation of the depth of ASL has not been reported previously. In this paper, we have used low-temperature scanning electron microscopy of rapidly frozen specimens of bovine tracheal epithelium to demonstrate alterations in the depth of ASL in response to the cholinergic agonist methacholine. We first established that methacholine selectively stimulated airway glands, with maximal secretion at approximately 2 min and a return to baseline within approximately 5 min. A 2-min exposure to methacholine increased the depth of ASL from 23 to 78 microns. Thereafter, depth decreased linearly with time, reaching 32 microns at 30 min. The initial increase in depth was blocked by bumetanide, an inhibitor of active chloride secretion, whereas the slow decline back to baseline was inhibited by amiloride, a blocker of active sodium absorption. We conclude that the methacholine-induced changes in ASL depth reflect transient gland secretion followed by liquid absorption across the surface epithelium.
气道的管腔表面衬有一层薄薄的气道表面液体（ASL）。此前尚未有关于ASL深度的生理调节的报道。在本文中，我们使用快速冷冻的牛气管上皮标本的低温扫描电子显微镜，来证明ASL深度对胆碱能激动剂乙酰甲胆碱的反应变化。我们首先确定，乙酰甲胆碱选择性刺激气道腺体，在约2分钟时分泌达到最大值，并在约5分钟内恢复到基线水平。暴露于乙酰甲胆碱2分钟使ASL深度从23微米增加到78微米。此后，深度随时间呈线性下降，在30分钟时达到32微米。深度的初始增加被布美他尼（一种活性氯分泌抑制剂）阻断，而缓慢下降回到基线则被阿米洛利（一种活性钠吸收阻滞剂）抑制。我们得出结论，乙酰甲胆碱诱导的ASL深度变化反映了短暂的腺体分泌，随后是液体通过表面上皮的吸收。
