| Abstract: | The influence of cyclic AMP on the metabolism of phosphatidylcholine, the major component of pulmonary surfactant was examined in a cell line (A549) with type 2 pneumonocyte characteristics. It was found that cyclic AMP increased both the total amount of phosphatidylcholine and disaturated phosphatidylcholine as well as the incorporation of 3H]choline into these fractions. The effect was specific for cyclic AMP since 5'-AMP, adenosine, and cyclic GMP did not alter phosphatidylcholine or disaturated phosphatidylcholine levels. Cyclic AMP had no effect on phosphatidylcholine and disaturated phosphatidylcholine metabolism in another non-type 2 human epithelial cell line (MA-160). Since the ability of various cyclic AMP analogs to increase phosphatidylcholine and disaturated phosphatidylcholine levels was correlated with their ability to activate protein kinase, it seems likely that a protein phosphorylation mechanism is involved in controlling phosphatidylcholine metabolism. |
