Pacht E R, Davis W B
Department of Medicine, Ohio State University 43210.
J Appl Physiol (1985). 1988 May;64(5):2092-9. doi: 10.1152/jappl.1988.64.5.2092.
Lung epithelial lining fluid (ELF) is a thin layer of plasma ultrafiltrate and locally secreted substances that may provide antioxidant protection and serve as a "front-line" defense for the lower respiratory tract epithelium. To characterize the antioxidant properties of ELF, young, healthy, nonsmoking volunteers underwent bronchoalveolar lavage with determination of ELF volumes and ELF proteins. ELF (greater than 0.4 ml) is a potent inhibitor of lipid peroxidation as measured by malondialdehyde (MDA) production in an in vitro iron-dependent assay system. Two serum proteins, transferrin and ceruloplasmin, were quantitated in ELF and found to be potent inhibitors of lipid peroxidation. Other ELF components, including vitamin E, vitamin C, and albumin, did not function as antioxidants in this system. Several experimental observations suggest that ELF transferrin was more important than ceruloplasmin in inhibiting lipid peroxidation: 1) ELF concentrations of transferrin were 20-fold higher than those for ceruloplasmin; 2) ELF antioxidant activity was abolished by preincubation with Fe3+; 3) ELF antioxidant activity was minimally affected by sodium azide, which is known to inhibit ceruloplasmin ferroxidase activity; and 4) ELF ceruloplasmin ferroxidase activity was virtually nondetectable. ELF possesses a significant antioxidant activity that may be important in vivo in protecting the lung from oxidant injury.
肺上皮衬液（ELF）是一层薄薄的血浆超滤液和局部分泌物质，可提供抗氧化保护，并作为下呼吸道上皮的“一线”防御。为了表征ELF的抗氧化特性，年轻、健康、不吸烟的志愿者接受了支气管肺泡灌洗，测定了ELF体积和ELF蛋白质。在体外铁依赖性测定系统中，通过丙二醛（MDA）生成量测量，ELF（大于0.4毫升）是脂质过氧化的有效抑制剂。在ELF中对两种血清蛋白转铁蛋白和铜蓝蛋白进行了定量，发现它们是脂质过氧化的有效抑制剂。其他ELF成分，包括维生素E、维生素C和白蛋白，在该系统中不作为抗氧化剂起作用。一些实验观察表明，在抑制脂质过氧化方面，ELF转铁蛋白比铜蓝蛋白更重要：1）ELF中转铁蛋白的浓度比铜蓝蛋白高20倍；2）与Fe3+预孵育可消除ELF的抗氧化活性；3）叠氮化钠（已知可抑制铜蓝蛋白铁氧化酶活性）对ELF抗氧化活性的影响最小；4）几乎检测不到ELF铜蓝蛋白铁氧化酶活性。ELF具有显著的抗氧化活性，这在体内保护肺部免受氧化损伤方面可能很重要。
