Sequential changes in phospholipid composition and synthesis in lungs exposed to nitrogen dioxide.

Abstract

Studies were performed to investigate the time course of biochemical and histologic changes in the lungs of rats after exposure to various concentrations of nitrogen dioxide. Special attention was given to identify lipid classes and the molecular species preferentially affected. Increased incorporation of thymidine, labeled with tritium, into deoxyribonucleic acid was first detected 12 hours after a 5-hour exposure to 40 ppm of nitrogen dioxide and reached a peak after 24 to 36 hours. The first histologic signs of a hyperplastic response in the alveolar ducts and alveoli became recognizable at 24 hours. In contrast, increased incorporation of palmitic acid, labeled with carbon-14, into phosphatidylcholine and the accumulation of this lipid class in the lungs could be detected as early as 6 hours after exposure to nitrogen dioxide. Lung wet weights and lung protein were also increased at this time. These findings suggest that the increase in phosphatidylcholine in the lungs exposed to nitrogen dioxide occu...