1203 NEUROGENIC MEDIATION OF AUGMENTED SURFACTANT SECRETION AT BIRTH

Abstract

The observation that alveolar lavage surfactant increases at birth following air or nitrogen breathing suggests that lung expansion affects net surfactant secretion (Ped Res 11:574, 1977). To study the mechanism of secretion we treated 13 pregnant rabbit does at 30 days gestation with repeated infusions of atropine (total, 2.4mg IV) or propranolol (total, 3-10mg IV) over a ½ hour period immediately prior to sacrifice. The pups were delivered by hysterotomy and divided into two groups. One group was sacrificed at birth without breathing. The remaining pups were sacrificed after 30 minutes hyperventilation induced by hypoxia (10-15% O2) or anoxia. Following sacrifice, alveolar surfactant was recovered by saline lavage and quantitatively estimated on a surface-tension balance (Science 169:603, 1970).These results provide additional support for the hypothesis that pulmonary surfactant secretion is stimulated following the onset of gas ventilation in newborns. We conclude that augmented surfactant secretion at birth is mediated by a neural mechanism. Furthermore, since the secretion is blocked by atropine and not propranolol we suggest secretion is under cholinergic control.