Inhibition of surfactant release from isolated Type II cells by compound 48/80.

Release of [3H]phosphatidylcholine from pulmonary Type II epithelial cells was stimulated by terbutaline, forskolin and cytochalasin D. Compound 48/80 inhibited both basal and agonist-stimulated release of [3H]PC. The IC50 for inhibition by compound 48/80 was 1-2 micrograms/ml, and was similar for inhibition of both basal and stimulated release of [3H]phosphatidylcholine. Inhibitory effects of 48/80 were noted following a 1 h exposure to compound 48/80 and persisted up to 3 h. The inhibitory effect of compound 48/80 was entirely reversed by removing compound 48/80 from the external milieu. Compound 48/80 had no effect on cytosolic cyclic AMP levels or lactate dehydrogenase release. Inhibition of surfactant release produced by compound 48/80 was unaffected by changes in extracellular calcium concentrations. Compound 48/80 is a non-toxic inhibitor of phosphatidylcholine release from Type II epithelial cells.