CORTICOSTEROIDS AND FETAL INTERVENTION INTERACT TO ALTER LUNG MATURATION IN PRETERM LAMBS

The relationship between cortisol infusion and time of fetal catheteri zation on postnatal lung function of prematurely delivered lambs was i nvestigated with the hypothesis that the intervention of catheterizati on would alter fetal responsiveness to the maturational effects of cor ticosteroids. Fetal catheterization was performed on d 117 or on d 122 of gestation. Cortisol or saline control infusions were begun on d 12 6, with delivery 60 h later on d 128. The animals were ventilated for 1.25 h after delivery, and compliance, the ventilation efficiency inde x, labeled albumin leak into and out of the lungs, alveolar and lung s aturated phosphatidylcholine and surfactant protein A were measured to evaluate lung performance and biochemical indicators of maturation. C ortisol improved compliance and ventilation efficiency and decreased l abeled albumin recovery without changing alveolar saturated phosphatid ylcholine or surfactant protein A in the animals catheterized at 122 d relative to 122-d saline-infused animals. However, the animals cathet erized at 117 d and infused with saline were as mature as assessed by compliance and ventilation efficiency as the 122-d cortisol-treated an imals. The 117-d cortisol-infused animals had significantly augmented lung function relative to either 117-d saline-infused or 122-d cortiso l-treated lambs and were the only group that had increased alveolar su rfactant protein A and lung saturated phosphatidylcholine pool sizes. This study demonstrates that the response of the fetal lung to a matur ational agent such as cortisol is dependent on the history of previous fetal interventions.