Gestational effects of corticosteroids and surfactant in ventilated rabbits.

Maternal corticosteroid treatments decreased lung protein leaks and increased the compliance responses to exogenous surfactant in 27-day preterm rabbits. We asked if maternal corticosteroid treatments at different gestational ages might alter these responses. Pregnant does were given 0.1 mg/kg betamethasone 48 and 24 h before study of the rabbits at 27, 28, and 29 days of gestational age and term newborns at 31 days of gestational age. Alternate rabbits at each gestation were treated with 50 mg/kg surfactant after delivery. Alveolar saturated phosphatidylcholine pool sizes increased with gestation similarly in control and corticosteroid-treated groups. Corticosteroids improved compliance relative to control values at 29 days of gestational age in animals not treated with surfactant and improved the compliance response to surfactant treatment at 27 and 28 days of gestational age. Corticosteroids decreased the leak of radiolabeled albumin to the lungs and alveolar washes at all preterm gestations with a maximum decrease to 16% of the control value at 29 days of gestation. Surfactant decreased this protein leak more effectively than did corticosteroids at the earlier gestations. There were potentially beneficial effects of corticosteroids either alone or together with surfactant at all preterm gestations studied. No protein leak or compliance effects of either treatment were noted in the term newborns.