THE EFFECT OF LABOR ON SURFACTANT SECRETION IN NEWBORN RABBIT LUNG SLICES

Surfactant secretion rate was studied in newborn rabbit lung slice model. Newborn rabbits were injected with [Me[methyl]-3H]choline and killed 4 h later. Secretion of phosphatidyl[Me-3H]choline was measured in washed slices from blood-free lungs. There was a developmental increase in the rate of secretion during the period 29-31 (full-term) days gestation. This was further increased by labor. Labor had no effect on the rate of incorporation of choline into phosphatidylcholine. Effect of labor was primarily on secretion rather than synthesis. Effect of labor on surfactant secretion could be mimicked by terbutaline and by prostaglandin E2. It was abolished by indomethacin and .beta.-blocking agents. Labor stimulates secretion of surfactant. Apparently, this effect is , at least in part, mediated by prostaglandins and .beta.-adrenergic agents, both of which increase physiologically during labor and birth.