TGF-BETA(3) INHIBITS THE INCREASED GENE EXPRESSIONS OF PULMONARY SURFACTANT PROTEINS INDUCED BY DEXAMETHASONE IN FETAL-RAT LUNG IN-VITRO

Objective To determine the effects of transforming growth factor-beta( 3)(TGF-beta(3)) on expressions of surfactant proteins (SPs). Methods N orthern blot hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) were employed to determine the SP-A, SP-B and SP-C m RNA levels of cultured lung explants and type I cells from fetal rat l ungs. Results TGF-beta(3) alone did not affect the expressions of SPs either in explants or in type I cells. However, TGF-beta(3) did inhibi t the increase of SP-B , SP-C mRNA levels caused by dexamethasone (100 nmol,/L), in a dose-dependent manner. Furthermore, TGF-beta(3), had n o direct inhibition on the increase of SP-BI SP-C mRNA induced by dexa methasone in type I cells, but had an indirect inhibitory effect media ted by fibroblasts. Conclusion TGF-beta(3) plays an important inhibito ry role in the development of pulmonary surfactant proteins. The prese nt study may provide a possible explanation for the unideal effect of glucocorticoids in the prevention of neonatal respiratory distress syn drome.