Stimulation of phosphatidylcholine synthesis by exogenous phosphatidylglycerol in primary cultures of type II pneumocytes.

We examined the effect of exogenous phospholipids on phosphatidylcholine synthesis in primary cultures of adult rat type II pneumocytes. Incubation of the cells with 10 microM phosphatidylglycerol for 2 h stimulated the rate of [3H]choline and [3H]glycerol incorporation into phosphatidylcholine by 72% and 50%, respectively. The effect appeared to be specific for phosphatidylcholine synthesis and was largely on the unsaturated species. Synthesis of disaturated phosphatidylcholine was little stimulated. The stimulatory effect of the lipid is unlikely to be a consequence of increased substrate, since it was not mimicked by glycerol, glycerol 3-phosphate or palmitic acid. Neither does it appear to be due to increased cell growth, since rates of protein and DNA synthesis were not increased. The relevance of these findings to surfactant turnover and reutilization warrants investigation.