Ip M P, Draisey T F, Thibert R J, Gagneja G L, Jasey G M
Clin Chem. 1977 Jan;23(1):35-40.
We describe a new and specific method for measurement of lecithin palmitic acid in amniotic fluid. Dipalmitoyl lecithin, the major alveolar surfactant, has previously been estimated by measuring the lecithin-sphingomyelin ratio, total lecithin, total phospholipid phosphorus, and (or) total palmitic acid. Our method is more specific for estimation of dipalmitoyl lecithin, because nonphospholipid sources of palmitic acid are removed by solvent extraction. Using a hexane/2-propanol/sulfuric acid system, we obviated the major interferences from triglycerides and free fatty acids. The palmitic acid derived from the phospholipid fraction is measured by gas-liquid chromatography of its methyl ester. No contribution appears to be made by sphingomyelin palmitic acid--probably owing to the mild hydrolysis conditions. The measured palmitic acid therefore appears to be derived from lecithins, principally dipalmitoyl lecithin. The value for palmitic acid determined by this method correlates well with the lecithin-sphingomyelin ratio and total phospholipid phosphorus. Infants are unlikely to develop respiratory distress syndrome when the measured palmitic acid in amniotic fluid exceeds 8.0 mg/liter, which corresponds to an lecithin-sphingomyelin ratio of 2.0.
我们描述了一种测量羊水卵磷脂棕榈酸的新的特异性方法。二棕榈酰卵磷脂是主要的肺泡表面活性物质，此前曾通过测量卵磷脂 - 鞘磷脂比值、总卵磷脂、总磷脂磷和（或）总棕榈酸来进行估算。我们的方法在估算二棕榈酰卵磷脂方面更具特异性，因为棕榈酸的非磷脂来源通过溶剂萃取被去除。使用己烷/2 - 丙醇/硫酸系统，我们消除了甘油三酯和游离脂肪酸的主要干扰。从磷脂部分衍生的棕榈酸通过其甲酯的气液色谱法进行测量。鞘磷脂棕榈酸似乎没有贡献——可能是由于温和的水解条件。因此，测得的棕榈酸似乎源自卵磷脂，主要是二棕榈酰卵磷脂。通过这种方法测定的棕榈酸值与卵磷脂 - 鞘磷脂比值和总磷脂磷密切相关。当羊水测得的棕榈酸超过8.0毫克/升时，婴儿不太可能发生呼吸窘迫综合征，这对应于卵磷脂 - 鞘磷脂比值为2.0。
