Abstract
It is well known that the surfactant system of the lung plays an important role in respiratory mechanics and its essential surfactant is phospholipids, particularly dipalmitoyllecithin. However, there are a few papers on the alteration of the surfactant under various pathological conditions. The purpose of this study is to investigate the effects of pulmonary circulatory and ventilatory disturbances on the surfactant system of the dog lung, especially on phospholipid.
Thirty-five dogs were divided into four groups; in the first group consisting of fifteen dogs the pulmonary vein was ligated, in the second of four dogs pulmonary artery was ligated, in the third of four dogs both pulmonary artery and vein were ligated, in the fourth of ten dogs bronchus was tied up at the hilum of left upper lobe. They were sacrificed in between 8 hours and 60 days after ligation. Lipid extraction and purification from the lung tissue was done by the Folch's method and total lipid content was determined gravimetrically. The individual phospholipids were identified and separated by thin layer chromatography, and phosphorus was assayed colorimetrically.
The fatty acid compositions of phosphatidylcholine were determined by gaschromatography. Surface tension was measured by a modified Wilhelmy surface balance. Histological studies of the lung tissues were carried out by hematoxylin-eosin staining.
Principal results obtained are as follows:
1) The mean contents of total lipid, phospholipid and phosphatidylcholine in lung tissues of thirty-five normal dogs are 151, 101 and 57mg/g dry tissue, respectively. Palmitate of phosphatidylcholine-fatty acid (PCFA) comprised 47% of the total. The average of γmin is 8.8 dynes/cm, and that of S1.38, indicating surface active.
2) Pulmonary vein ligation induces congestive atelectasis. Total lipid, phospholipid, and phosphatidylcholine contents are found decreased remarkably from 8 to 96 hours after the ligation, but almost recovered after 30 to 60 days. C16-0 of PCFA reduces slightly from 24 to 96 hours after the ligation. Surface activity is not demonstrated after 24 to 96 hours of ligation, and returns to normal 30 days after ligation.
3) Pulmonary artery ligation and pulmonary artery-and-vein ligation causes almost similar changes, but the decrease of C16-0 of PCFA is prominent at 96 hours after the ligation. In dogs with pulmonary artery-and-vein ligation, surface activity dose not recover in 30 days and the fractional content of each lipid shows decrement. They are considered to show the delay of recovery.
4) In the group of bronchus ligation, total lipid, phospholipid and phosphatidylcholine contents reduce approximately 75% of those of non-ligated lobes and surface activity is decreased 96 hours after the ligation. Although lipid content returns to about 90% of that of normal lungs 30 days after the ligation, surface activity dose not recover in four out of five animals.
5) Two additional sampling methods for the surfactant are comparatively evaluated with that described above. They are bronchial lavage with saline and saline extract from minced lung tissue. After lyophilization of each sample, lipids are extracted with chloroform-methanol. All of these three methods are discussed on their characteristics and are confirmed to be useful for the lung surfactant analysis.
These results indicate that the pulmonary blood flow is essential for the maintenance of lung surfactant system.
