Could a combined administration of dexamethasone and 3,5-dimethyl-3′-isopropyl-L-thyronine (DIMIT) be a more effective alternative to dexamethasone alone in the prevention of RDS?

Objective: To test whether the combined application of dexamethasone (DEXA) and 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) induces the synthesis of surfactant protein A (SP-A) mRNA at a higher rate than both substances given alone? Study design: Organoid culture of fetal rat lungs (Wistar rats; day 19 of gestation) was prepared. After 48 h of incubation we added DEXA (10(-5), 10(-7), 10(-8) and 10(-9) mol/l), DIMIT (10(-5), 10(-7) and 10(-9) mol/l) and the combination of DEXA in 10(-8) mol/l with various concentrations of DIMIT. After another 48 h of incubation, northern blot and hybridization with a P-32-labeled SP-A cDNA probe was performed. One-way-variance-analysis with a Scheffe-test, Levene-test and one-sample-t-test were used for statistical analysis. Results: DEXA alone above 10(-8) mol/l resulted in a significant increase, DIMIT resulted in a decrease of SP-A mRNA induction. Combined application of DIMIT and DEXA resulted in a significant increase compared to the controls. Compared to DEXA alone in 10(-8) mol/l, we found an increased induction, but the data were not significant. Conclusions: The combined application of DEXA and DIMIT shows a higher induction of SP-A mRNA than both drugs given alone. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.