SURFACE-PROPERTIES OF RAT PULMONARY SURFACTANT STUDIED WITH THE CAPTIVE BUBBLE METHOD - ADSORPTION, HYSTERESIS, STABILITY
SURFACE-PROPERTIES OF RAT PULMONARY SURFACTANT STUDIED WITH THE CAPTIVE BUBBLE METHOD - ADSORPTION, HYSTERESIS, STABILITY
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DOI：
10.1016/0005-2736(92)90066-u
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发表时间：
1992-01-10
期刊：
影响因子：
--
通讯作者：
GREEN, F
中科院分区：
文献类型：
--
作者：
SCHURCH, S;BACHOFEN, H;GREEN, F
用一种新型的仪器测量了肺表面活性剂的表面张力-面积关系，该仪器包含一个大小可控的无泄漏捕获气泡。研究了磷脂浓度为50、200和400 μ g/ml时大鼠肺表面活性剂的活性。在最高浓度下，吸附迅速，在1 s内达到表面张力低于30 mN/m，而在最低浓度下，大约需要3 min。在第一次准静态或动态压缩后，通过膜面积减少约50%，可以获得低于1 mN/m的稳定表面张力。经过三到四个循环后，表面张力-面积关系趋于平稳，张力从25-30下降到约1 mN/m，膜面积减少不到20%。只要膜不因面积进一步缩小而塌陷，迟滞就可以忽略不计。在这些条件下，薄膜可以循环超过20分钟，而表面活性没有任何明显的损失。经过三到四个连续的循环后，表面活性剂薄膜表现出原位肺泡表面的低表面张力、崩溃率和可压缩性特征。值得注意的是，在俘获气泡中，表面张力和面积是相互关联的，这可能会促进低而稳定的表面张力。如果由于机械振动或表面活性剂不稳定，俘获气泡的表面张力突然增加（“咔嚓”声），气泡形状就会从扁平变为球形。与此相关的等体积表面积的减少阻止了表面张力的上升，而表面张力的上升与在等面积情况下的上升一样多。这种反馈机制也可能对稳定低肺容量时的肺泡表面张力有有利作用。
Surface tension-area relations from pulmonary surfactant were obtained with a new apparatus that contains a leak free captive bubble of controllable size. Rat pulmonary surfactant was studied at phospholipid concentrations of 50, 200 and 400-mu-g/ml. At the highest concentration, adsorption was rapid, reaching surface tensions below 30 mN/m within 1 s, while at the lowest concentration, approximately 3 min were required. Upon a first quasi static or dynamic compression, stable surface tensions below 1 mN/m could be obtained by a film area reduction of approximately 50%. After three to four cycles the surface tension-area relations became stationary, and the tension fell from 25-30 to approximately 1 mN/m for a film area reduction of less than 20%. Hysteresis became negligible, provided the films were not collapsed by further area reduction. Under these conditions, the films could be cycled for more than 20 min without any noticeable loss in surface activity. After only three to four consecutive cycles, surfactant films exhibited the low surface tensions, collapse rates and compressibilities characteristic of alveolar surfaces in situ. Remarkably, surface tension and area are interrelated in the captive bubble which may promote low and stable surface tensions. If the surface tension of the captive bubble suddenly increases ('click') because of mechanical vibration or unstable surfactant, the bubble shape changes from flat to more spherical. The associated isovolumetric decrease in surface area prevents the surface tension from rising as much as it would have in a constant-area situation. This feedback mechanism may also have a favorable effect in stabilizing alveolar surface tension at low lung volumes.