The distribution of 14C-arachidonic acid in hamster lungs is sensitive to quinacrine

Isolated hamster lungs were labelled with 14C-arachidonic acid. When the lungs were ventilated with a respirator only a small amount of radioactivity was released to the perfusion effluent. This release was not changed significantly by pulmonary infusion of quinacrine (0.5 mM), a known inhibitor of phospholipase A2. After the perfusion about 75% of the radioactivity in the lungs was in phospholipids, mainly in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol and to a lesser degree in phosphatidylserine and phosphatidic acid. About one fourth of the radioactivity was in neutral lipids (tri- and diacylglycerols) and as free unmetabolized 14C-arachidonic acid. Pulmonary infusion of quinacrine increased the amount of radioactivity in diacylglycerols and phosphatidylinositol but had no effect on that in phosphatidylcholine, phosphatidylserine, phosphatidic acid and triacylglycerols. The amount of radioactivity in phosphatidylethanolamine was decreased by quinacrine and increased in the vicinity of an unidentified phospholipid-quinacrine complex. The present study indicates that the distribution of 14C-arachidonic acid in hamster lung lipids is sensitive to quinacrine. The detected changes can, however, not be explained by an overall inhibition of phospholipase A2 activities.