Abstract
Pulmonary stability increases within 30 minutes of birth in newborn rabbits, suggesting enhanced surfactant release after birth (J. Appl. Physiol. 37:809, 1974). The mechanism for this is unknown but circulating catecholamines and lung expansion per se (Fed. Proc. 32:1018, 1973) have been implicated. To study the effect of lung expansion we delivered by hysterotomy 7 litters of rabbit pups at 30 days gestation and divided them into 3 groups which were sacrificed: a) after 30 minutes air-breathing, b)after 30 minutes nitrogen-breathing, or c) after 30 minutes tracheal occlusion. Each group was compared to a littermate group sacrificed at birth. Groups b) and c) continued respiratory efforts for 30 minutes despite progressive asphyxia. Following sacrifice alveolar sufactant was recovered by saline lavage and measured quantitatively on a surface-tension balance as described by Clements (Science 169:603, 1970). Surfactant concentration at birth was 140±44μg/0.1gm dry lung and rose to 192±40μg after 30 minutes air-breathing (p<.03). Surfactant also increased in the nitrogen-breathing pups (312±108 vs 185±70 in littermate controls; p<.05) but not in the occluded group (178±41 vs 177±52). These results confirm the hypothesis that surfactant release is enhanced at birth. Furthermore, the data suggest that lung expansion, rather than circulating humoral factors associated with stress, is responsible for augmented surfactant release following birth.
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Lawson, E., Bird-Well, R., Huang, P. et al. AUGMENTATION OF PULMONARY SURFACTANT RELEASE BY LUNG EXPANSION AT BIRTH. Pediatr Res 11, 574 (1977). https://doi.org/10.1203/00006450-197704000-01223
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DOI: https://doi.org/10.1203/00006450-197704000-01223