Antenatal dexamethasone enhances surfactant protein synthesis in the hypoplastic lung of nitrofen-induced diaphragmatic hernia in rats

Background/Purpose: Pulmonary hypoplasia is one of the main causes for the high mortality rate in patients with congenital diaphragmatic hernia (CDH). The expression of surfactant protein A in the hypoplastic CDH lung is redu ced, and its concentration is decreased in the amniotic fluid of pregnancie s complicated by CDH. In a CDH experimental model, prenatal glucocorticoid treatment has proved its efficacy in correcting the parameters of pulmonary biochemical and morphologic immaturity. The aim of this study was to inves tigate whether maternal administration of dexamethasone has any effect on t he expression of surfactant protein A and surfactant protein B in nitrofen- induced experimental CDH rat model. Methods: CDH was induced in pregnant rats after administration of 100 mg of nitrofen on day 9.5 of gestation (term, 22 days). Dexamethasone (Dex, 0.25 mg/kg) was given by intraperitoneal injection on days 18.5 and 19.5 of ges tation. Cesarean section was performed on day 21 of gestation. The fetuses were divided into 3 groups: group I, control (n = 16); group II, nitrofen-i nduced CDH (n = 16); group III, nitrofen-induced CDH with antenatal Dex tre atment (n = 16). Indirect immunohistochemistry was performed using alkaline -phosphatase-coagulated streptavidin using anti-SP-A and anti-SP-B polyclon al antibodies. Reverse transcription polymerase chain reaction (RT-PCR) was performed to evaluate relative amount of SP-A and SP-B mRNA expression. Results: In the CDH lung (group II) we observed a markedly reduced number o f type II pneumocytes positive for SP-A, and SP-B was increased to a level close to that of the control group. The relative amount of SP-A and SP-B wa s reduced significantly in group II compared with controls (P<.05) and sign ificantly increased in group III compared with group II animals(P<.01). Conclusion: These results suggest that antenatal glucocorticoid treatment i ncreases the production of surfactant proteins in the CDH hypoplastic lung. J Pediatr Surg 35:1468-1473. Copyright (C) 2000 by W.B. Saunders Company.