Holm B A, Wang Z, Egan E A, Notter R H
Department of Obstetrics@Gynecology, State University of New York at Buffalo, New York 14214, USA.
Pediatr Res. 1996 May;39(5):805-11. doi: 10.1203/00006450-199605000-00010.
The content of dipalmitoyl phophatidylcholine (DPPC) in the phosphatidylcholine (PC) fraction of calf lung surfactant extract (CLSE) is measured by gas chromatography (GC) and estimated from the widely used osmium tetroxide assay for disaturated phosphatidylcholine (DSPC). The surface-active properties of model phospholipid/apoprotein surfactants with varying DPPC content are also defined and compared relative to CLSE. GC analysis of fatty acids in PC isolated from CLSE indicated a possible range of 30 to 65% for DPPC content depending on C16:0 fatty chain mismatching, and further studies using phospholipase A2 treatment indicated an actual DPPC content < or = 41%. The osmium tetroxide assay gave a very high value of 70% for the DSPC content of surfactant PC, and experiments with synthetic phospholipids demonstrated that this assay responded inappropriately in the presence of monounsaturated PC, leading to falsely elevated DSPC values. The influence of DPPC content on adsorption and film behavior was investigated in model surfactants containing 40, 60, and 80% DPPC (DPPC/egg PC/egg PG, 40:50:10, 60:30:10, and 80:10:10 by mol) combined with 1.3% hydrophobic surfactant protein (SP)-B and -C. The biophysical properties of the model surfactant with 40% DPPC were found to be closer to CLSE than those of mixtures with 60 or 80% DPPC. The adsorption of dispersions containing 40% DPPC with 1.3% SP-B, C was almost identical to CLSE and was improved in rate and magnitude compared with the mixtures with higher DPPC content (60 or 80%). In Wilhelmy balance studies of cycled films, respreading was increased and maximum surface pressure was decreased for the 40% versus higher DPPC content mixtures, again approaching CLSE in behavior. All synthetic phospholipid (SPL):SP mixtures lowered surface tension to < 1 mN/m in oscillating bubble studies at physiologic cycling rate (20 cpm), but the 40% DPPC mixture had a time dependent most closely matching that of CLSE. Our measured DPPC content near 40% for lung surfactant PC, and the similarly high activity of a related synthetic phospholipid/apoprotein model mixture, suggest that exogenous surfactants with relatively low DPPC contents might be important for future study and development.
通过气相色谱法（GC）测定小牛肺表面活性剂提取物（CLSE）的磷脂酰胆碱（PC）组分中双棕榈酰磷脂酰胆碱（DPPC）的含量，并根据广泛使用的用于测定二饱和磷脂酰胆碱（DSPC）的四氧化锇法进行估算。还定义了具有不同DPPC含量的模型磷脂/载脂蛋白表面活性剂的表面活性特性，并与CLSE进行了比较。对从CLSE中分离出的PC中的脂肪酸进行GC分析表明，由于C16:0脂肪酸不匹配，DPPC含量可能在30%至65%的范围内，进一步使用磷脂酶A2处理的研究表明实际DPPC含量≤41%。四氧化锇法测得表面活性剂PC的DSPC含量非常高，为70%，并且用合成磷脂进行的实验表明，在存在单不饱和PC的情况下，该测定反应不当，导致DSPC值错误升高。在含有40%、60%和80% DPPC（DPPC/鸡蛋PC/鸡蛋PG，摩尔比为40:50:10、60:30:10和80:10:10）并结合1.3%疏水性表面活性剂蛋白（SP）-B和-C的模型表面活性剂中，研究了DPPC含量对吸附和膜行为的影响。发现含40% DPPC的模型表面活性剂的生物物理特性比含60%或80% DPPC混合物的更接近CLSE。含40% DPPC与1.3% SP-B、C的分散体的吸附几乎与CLSE相同，并与含较高DPPC含量（60%或80%）的混合物相比在速率和程度上有所改善。在循环膜的Wilhelmy天平研究中，与较高DPPC含量的混合物相比，含40% DPPC的混合物的再铺展增加且最大表面压力降低，其行为再次接近CLSE。在生理循环速率（20次/分钟）的振荡气泡研究中所有合成磷脂（SPL）:SP混合物都能将表面张力降低至<1 mN/m，但含40% DPPC的混合物具有与CLSE最密切匹配的时间依赖性。我们测得肺表面活性剂PC的DPPC含量接近40%，以及相关合成磷脂/载脂蛋白模型混合物同样具有高活性，这表明具有相对较低DPPC含量的外源性表面活性剂可能对未来的研究和开发很重要。
