CHANGES IN CDP-DIGLYCERIDE-INOSITOL TRANSFERASE-ACTIVITY DURING RABBIT LUNG DEVELOPMENT

During fetal and neonatal development the specific activity of the enzyme, CDP- diglyceride:inositol transferase in rabbit lung tissue increased 8- to 9-fold from day 17 of gestation to adulthood. This developmental increase in enzyme activity was not specific for ling tissue since a similar increase was also observed in liver tissue. The properties of CDP-diglyceride:inositol transferase in microsomes prepared from either fetal or adult rabbit lung tissue appeared to be the same. The increase in CDP-diglyceride:ino- sitol transferase activity in rabbit lung tissue during development appeared to be reflective of synthesis of new enzyme rather than activation of pre-existing enzyme. SPECULATION: CDP-cfiglyceride:inositol transferase activity in fetal rabbit lung tissue increases at a stage in development when the phosphatidylinositol content of lung surfactant is decreasing. In the presence of CMP, CDP-diglyceride:inositol transferase catalyzes the synthesis of CDP-diglyceride from phosphatidylinositol. We speculate that the increased CDP-diglyceride:inositol transferase activity, in conjunction with elevated intracellular CMP levels resulting from accelerated phosphatidylcholine biosynthesis, provides a pool of CDP-diglyceride for phosphatidylglycerol biosynthesis during the latter stages of fetal lung maturation. © 1979 International Pediatric Research Foundation, Inc.