King R J
J Appl Physiol Respir Environ Exerc Physiol. 1982 Jul;53(1):1-8. doi: 10.1152/jappl.1982.53.1.1.
Pulmonary surfactant reduces the surface tension of the alveolar air-liquid interface, thereby providing mechanical stability and preventing alveolar atelectasis. More than 50% of surfactant is dipalmitoyl phosphatidylcholine, a material that is capable of reducing the surface tension of the alveolar interface to uniquely low values. The functions of the remaining 25% unsaturated phosphatidylcholines, 5-10% phosphatidylglycerol, 5% cholesterol, and 8-10% protein are unknown. Surfactant is synthesized by alveolar epithelial type II cells and is probably secreted as a lipoprotein complex. Lamellar bodies, which distinguish type II cells, are likely to be intracellular sites of transport of processing. The catabolism of surfactant after it is secreted into the alveolar lumen is complicated and involves different turnover times for the phosphatidylcholines, phosphatidylglycerol, and the proteins. The metabolic events are under hormonal control and may involve an interplay between beta-adrenergic agonists cAMP, and prostaglandins. In disease, such as the neonatal and adult respiratory distress syndromes, derangements in the metabolic processes may produce surfactant that is abnormal with respect to its chemical and physical properties.
肺表面活性物质可降低肺泡气液界面的表面张力，从而提供机械稳定性并防止肺泡萎陷。超过50%的表面活性物质是二棕榈酰磷脂酰胆碱，这种物质能够将肺泡界面的表面张力降低到极低的值。其余25%的不饱和磷脂酰胆碱、5 - 10%的磷脂酰甘油、5%的胆固醇以及8 - 10%的蛋白质的功能尚不清楚。表面活性物质由肺泡II型上皮细胞合成，可能以脂蛋白复合物的形式分泌。层状体是II型细胞的特征性结构，可能是加工运输的细胞内位点。表面活性物质分泌到肺泡腔后，其分解代谢过程复杂，不同的磷脂酰胆碱、磷脂酰甘油和蛋白质的周转时间不同。这些代谢事件受激素控制，可能涉及β - 肾上腺素能激动剂、环磷酸腺苷（cAMP）和前列腺素之间的相互作用。在疾病中，如新生儿和成人呼吸窘迫综合征，代谢过程的紊乱可能产生化学和物理性质异常的表面活性物质。
