| Abstract: | Developing rabbits reutilize the phosphatidylcholine of surfactant with an efficiency of about 95%. The efficiency of reutilization of other components of surfactant have not been determined. 3-day-old rabbits were injected intratracheally with 3H]dipalmitoylphosphatidylcholine (DPPC) mixed with unlabeled natural surfactant and either disaturated 32P]phosphatidylglycerol (DSPG) or 14C]dipalmitoylphosphatidyl-ethanolamine (DPPE). The recovery of 3H]DPPC, 14C]DPPE, and 32P]DSPG in the alveolar wash was measured at different times after injection. By plotting the ratio of 32P]DSPG to 3H]DPPC or 14C]DPPE to 3H]DPPC counts/min in the alveolar wash vs. time after injection we showed that these two phospholipids are reutilized less efficiently than phosphatidylcholine. Based on other studies, several assumptions were made about the kinetics of surfactant phosphatidylethanolamine and phosphatidylglycerol. From the slopes of the semilog plots of total 14C]DPPE and total 32P]DSPG counts/min in the alveolar wash vs. time and these assumptions, we determined that these two phospholipids were reutilized at an efficiency of only 79%. |
