Keller G H, Ladda R L
Proc Natl Acad Sci U S A. 1979 Aug;76(8):4102-6. doi: 10.1073/pnas.76.8.4102.
Rat lung slices and isolated rat lung cells were used to study the secretion of phosphatidylcholine by the lung in vitro. The rate of incorporation of [(3)H]choline by lung slices was 20-fold greater than by liver slices and 4-fold greater in lung cells compared to confluent skin fibroblasts. Labeling lung slices or cells with [(3)H]choline for up to 8 hr failed to reveal a significant amount of labeled phosphatidylcholine in the medium of either system compared to the medium from liver slice or fibroblast controls. Labeling of isolated lung cells for up to 24 hr, with or without 10% fetal calf serum, also showed no significant difference in the amount of labeled phosphatidylcholine in the medium compared to control fibroblast cultures. Washing labeled lung slices or cells with a nonlysing concentration of Triton X-100 (0.05%) did not selectively release labeled phosphatidylcholine, indicating that any secreted phosphatidylcholine did not adhere to the surface of the lung slices or cells. Experiments were performed to determine whether the small amount of phosphatidylcholine in the medium and detergent-released phosphatidylcholine was similar to the tissue and cell phosphatidylcholine. The saturated fatty acid composition of the phosphatidylcholine released by Triton X-100 and in the medium (from lung slices) was identical to that of the tissue phosphatidylcholine. In addition, the relative labeling rates of the phospholipids released by Triton X-100 and in the medium (labeled with [(14)C]glycerol) were identical to those of the tissue and cell phospholipids. Based on these results, we conclude that phosphatidylcholine is not secreted by lung slices and lung cells in large amounts compared to controls. The implication of these data is that pulmonary surfactant material may actually not be secreted by the lung in vitro, and perhaps in vivo, in the manner that is currently generally accepted.
使用大鼠肺切片和分离的大鼠肺细胞来研究肺在体外分泌磷脂酰胆碱的情况。肺切片对[（3）H]胆碱的摄取率比肝切片高20倍，与汇合的皮肤成纤维细胞相比，肺细胞中的摄取率高4倍。用[（3）H]胆碱标记肺切片或细胞长达8小时，与来自肝切片或成纤维细胞对照的培养基相比，在这两种系统的培养基中均未发现大量标记的磷脂酰胆碱。对分离的肺细胞进行长达24小时的标记，无论有无10%胎牛血清，与对照成纤维细胞培养物相比，培养基中标记的磷脂酰胆碱量也没有显著差异。用非裂解浓度的 Triton X-100（0.05%）洗涤标记的肺切片或细胞，不会选择性地释放标记的磷脂酰胆碱，这表明任何分泌的磷脂酰胆碱都不会附着在肺切片或细胞表面。进行实验以确定培养基中少量的磷脂酰胆碱和去污剂释放的磷脂酰胆碱是否与组织和细胞中的磷脂酰胆碱相似。Triton X-100释放的以及培养基中（来自肺切片）的磷脂酰胆碱的饱和脂肪酸组成与组织磷脂酰胆碱相同。此外，Triton X-100释放的以及培养基中（用[（14）C]甘油标记）的磷脂的相对标记率与组织和细胞磷脂的相对标记率相同。基于这些结果，我们得出结论，与对照相比，肺切片和肺细胞不会大量分泌磷脂酰胆碱。这些数据的含义是，肺表面活性物质实际上可能不会以目前普遍接受的方式在体外分泌，也许在体内也不会。
