Corticosteroids and intratracheal surfactant both alter the distribution between the airways and lung tissue of intratracheally administered radiolabeled phosphatidylcholine in the preterm rabbit.

Developmental differences exist regarding quantitative aspects of surfactant phosphatidylcholine clearance from the alveolar space and its subsequent reutilization. We wished to further extend observations of this nature to prematurely delivered rabbits undergoing mechanical ventilation. In addition we tested the hypothesis that prenatal corticosteroid exposure and/or intratracheal surfactant at birth would produce alterations in the lung's clearance of phosphatidylcholine from the airways. Pregnant does were injected with either Ringer's lactate or betamethasone on days 25 and 26 of gestation. Fetuses were delivered at 27 days and given by intratracheal injection either surfactant or one-half strength Ringer's lactate, both of which were trace labeled with [3H]phosphatidylcholine. Fetuses then underwent mechanical ventilation for periods of time ranging from 10 to 120 min. Following ventilation, alveolar lavage and lung tissue were examined to determine the distribution of [3H]phosphatidylcholine between these two compartments. Antenatal corticosteroid exposure was associated with decreased recovery of the radiolabel from the alveolar space and increased recovery of the label from the lung tissue in comparison to control fetuses. Intratracheal surfactant was associated with persistence of the radiolabel within the alveolar space. Therapy with both of these modalities produced a radiolabel distribution that resembled that seen in fetuses receiving intratracheal surfactant alone.