Enhanced Proteolytic Activity at pH 2.0 in Lungs of Infants Dying from Hyaline Membrane Disease (HMD). ∗

Summary

Extracts of lung tissues from newborn infants contain variable amounts of proteolytic activity. At pH 2 lungs with hyaline membrane disease of the newborn exhibit more activity than control lungs without the disease. Exposure to pH 8.5 does not abolish this activity. Likewise, preliminary studies indicate that neonatal gastric juice is not inactivated by pH 8.5 in contrast to adult gastric juice and hog pepsin. The nature of this proteolytic activity is discussed with reference to lysosomal cathepsin and fetal pepsin from aspirated gastric juice and their possible rôles in the genesis of hyaline membrane disease of the newborn.