EFFECT OF ESCHERICHIA-COLI LIPOPOLYSACCHARIDE ON SURFACTANT SECRETIONIN PRIMARY CULTURES OF RAT TYPE-II PNEUMOCYTES

The purpose of this study is to evaluate the effect of the Escherichia coli lipopolysaccharide on the secretion of phosphatidylcholine, the principal component of pulmonary surfactant, in primary cultures of ra t alveolar type II pneumocytes. Lipopolysaccharide stimulated phosphat idylcholine secretion in a time- and dose-dependent manner. At a conce ntration of 200 mu g/ml, lipopolysaccharide stimulated the release of phosphatidylcholine 4-fold over the basal secretory rate, and the conc entration producing half the maximal response was 20 mu g/ml. The stim ulatory effect of lipopolysaccharide on phosphatidylcholine secretion was additive to that of the protein kinase C activator TPA, which is a potent stimulator of surfactant secretion. Lipopolysaccharide did not activate protein kinase C, which suggests that stimulation of phospha tidylcholine secretion by the endotoxin was through a mechanism indepe ndent of protein kinase C activation.