Abstract
Surface activity of alveolar lining layer has been investigated with modified Wilhelmy balance which is getting popular, but there were only a few papers regarding the fundamental problems.
In this studies we investigated the influences of rate of compression-expansion cycle, blood, and the concentration of lung extract on surface activity.
Maximal surface tension increased as the rate of compression-expansion cycles increased which was sinusoidal. The mean of γ max was 57.6 and 39.8dynes/cm at the rate of 1min. per cycle and of 10min, per cycle respectively. However, γmin was not influenced by change in the rate of cycling.
There were no significant differences in γ max, γmin, and S among three lung extracts; bronchial washing, the lung extract produced by mincing lung tissue, and lung extract produced by mincing blood-free lung tissue. The mixing of 10cc of blood with the lung extract made from 2g of lung tissue in 20cc of saline increased γmin in 5 out of 15 extracts. These five extracts were surface-active (γmin<15dynes/cm) in the concention of 2g of lung tissue in 30cc of saline, but inactive (γmin>15dynes/cm) in the concentration of 1g of lung tissue in 30cc of saline.
γmin of all 12 extracts were less than 15dynes/cm in the concentration of 2g or 3g of lung tissue in 30cc of saline, but γmin showed more than 15dynes/cm in 5 out of the 12 extracts in the concentration of 1g of lung tissue in 30cc of saline and in 10 out of them in the concentration of 0.5g of lung tissue in 30cc of saline.
The relationship between γmin and stability ratio (SR) measured by Pattle's method was investigated in normal rabbit lung and the lung with ligated pulmonary vein. The lung with γmin less than 15dynes/cm had SR more than 0.7 and the value of SR decreased and reached to nearly O as the γmin increased.
