INFLUENCE OF INSULIN AND PALMITIC ACID CONCENTRATION ON PULMONARY SURFACTANT SYNTHESIS

We have tested the influence of palmitic acid and insulin on the rate of pulmonary surfactant synthesis in the isolated, perfused rat lung. We assessed the rate of surfactant synthesis by determination of the incorporation of [9,10-3H]palmitic acid into surfactant isolated from lung homogenate by differential and isopynic centrifugations (King and Clements, Amer. J. Physiol., 233, 707-714, 1972). We found that an increase in the palmitic acid concentration from 0.5 to 1.5 mM doubled the rate of surfactant synthesis. Insulin (8 × 10-3 U/ml) added to perfusion medium containing 0.5 mM palmitic acid had a slight, but significant (P < 0.05) stimulatory effect on surfactant synthesis. These results are consistent with the hypothesis that insulin influences the rate of surfactant synthesis via its inhibitory action on lipolysis, rather than via a direct inhibition of the rate of surfactant synthesis. © 1979.