Pre- and postnatal stimulation of pulmonary surfactant protein D by in vivo dexamethasone treatment of rats.

Fetal (days 18 and 20 of gestation), neonatal (days 0, 2 and 4 of neonate) and adult rats were injected with dexamethasone (1 mg/kg) in vivo and 24 hours later the effect on the contents of surfactant protein D (SP-D) in the rat lungs were examined in comparison with surfactant protein A, disaturated phosphatidylcholine and phosphatidylglycerol. In vivo dexamethasone treatment resulted in significant increases of SP-D content as the other 3 components of surfactant in both fetuses and neonates, but not in adults. Responsiveness to glucocorticoid treatment on SP-D content was maximum on day 1 of neonate (2.7 times control value). The contents of surfactant components examined tend to respond better to steroid in postnatal rats. These data demonstrated that glucocorticoid treatment in vivo for short durations exhibits the stimulatory effect on the contents of SP-D in the fetal and neonatal rat lungs.