Effect of isoxsuprine on fetal lung surfactant in rabbits

To examine the effect of beta adrenergic drugs on fetal lung development, we administered isoxsuprine to pregnant rabbits for 24 hr and measured indices of pulmonary surfactant synthesis, storage, and release in rabbit fetuses at 26 days gestation. Incorporation of radiolabeled choline into total and disaturated phosphatidylcholine was measured in vitro in fetal lung slices. There was a significant increase in the rate of choline incorporation into disaturated phosphatidylcholine in the isoxsuprine-treated group and a tendency toward an increased incorporation into total phosphatidylcholine as well. We also observed an increase in the pulmonary phospholipid reservoir as evidenced by a significant increase in total lung disaturated phosphatidylcholine and a trend toward higher total lung phosphatidylcholine in the isoxsuprine group. In addition, there was a significant increase in lung lavage L/S ratio in the treated fetuses and in lung deflation stability determined by pressure volume curve. We conclude that isoxsuprine increases synthesis, storage, and release of surfactant in rabbit fetuses at 26 days gestation.