| Abstract: | 32P-saturated phosphatidylcholine was added to 3H]choline-labeled natural surfactant and the mixture was injected intratracheally into 87 adult rabbits. The rabbits were also given 14C]palmitate intravenously at the same time. Rabbits were killed in groups from 10 min to 72 h after injection. In each rabbit we measured the total recovered 3H]phosphatidylcholine (PC) in the alveolar wash, the ratio of 3H]PC to 32P]PC in the alveolar wash, and the specific activity of 14C]PC in the alveolar wash and lamellar bodies. Values were averaged for all rabbits killed at the same times and smooth curves were fit to the data by computer. From the intravenous 14C]palmitate data we calculated a turnover time for alveolar PC of 6.0 h. From the intratracheal labeling data, we calculated a turnover time for alveolar PC of 5.7 h and determined that alveolar PC was reutilized at an efficiency of only 23%. We also concluded that this reutilization occurred as intact molecules. |
