Abstract
Phospholipase A activity was investigated in rat lung homogenate using a-3H-palmitoyl lecithin, a-14C-palmitoyl-phosphatidylethanolamine and 2-3H-glycerol labeled phosphatidylethanolamine as substrates. The activity was estimated by measuring the release of radioactive products (fatty acids, water soluble compounds and lysophospholipids). It was noted that lung hydrolase accumulated more lyso-compounds in comparison with that of the liver. The hydrolysis proceeded linearly during the 6 hr incubation. The enzyme did not require Ca++ ions, and was somewhat inhibited at higher concentrations of Ca++. Sodium deoxylcholate inhibited both the release of fatty acids and lysophospholipids. Half of the total activity of the lung was found in the supernatant fraction, while the liver supernatant showed only a quarter of the total activity. The 14C/3H ratios of the lysophosphatidylethanolamine suggested that phospholipase A2 activity was higher than phospholipase A1 activity in the lung.
