pH-Dependent Changes in Surface Activity of Lung Extracts 1

Abstract

Summary

We have studied the effect of various KOH concentrations and pH alterations on dog and rabbit lung tissue extracts. Extracts in KOH had a higher minimal surface tension than saline extracts. Most KC1 extracts were normal. Twelve lungs were extracted with NaOH, and an additional seven saline extracts were alkalinized with 10% NaOH solution. Sixteen of these showed a marked rise in minimal surface tension. In the three that did not, the contour of the tension-area curve changed markedly, with more gradual slope and narrower hysteresis loop. Minimal surface tension was consistently raised with addition of K₂CO₃ and NaHCO₃ as well. Similar abnormalities were produced by lowering pH with 0.1 N HCl.

The pH of 26 lung extracts was also altered with phosphate buffer solution. Minimal surface tension changes were not so extreme, but there was a slight positive correlation of pH with minimal surface tension. The pH of saline extract of normal lung tissues and of the lung itself was slightly lower than normal blood pH.

This study demonstrates an influence of pH changes on surface activity of normal lung extract. The possibility of a functional role of pH in the lung must be considered.