Objective: To determine the effects of betamethasone and thyroid releasing hormone (TRH) on morphologic fetal rabbit lung maturation when administered separately and in combination.
Material and methods: Twenty-five pregnant rabbits were divided into five groups. Study groups were as follows: TRH or betamethasone alone (between 24 and 27th days of gestation), TRH + betamethasone or betamethasone + TRH (second dose of drugs were added in the last 2 days), and the control. The pregnancies were terminated on the 27th day of gestation. Weights and volumes of the fetal lungs were determined and the results were compared.
Results: Mean lung weights in all treatment groups were significantly heavier than controls (P < 0.05). The differences between mean lung weights of TRH alone, TRH + betamethasone, and betamethasone alone groups were not statistically significant (P > 0.05), but the mean lung weight of betamethasone + TRH group was significantly lower than the other treatment groups (P < 0.05). Mean lung volume of TRH alone group was significantly higher than control group; however, there were no significant differences between other treatment groups and the control. No correlation was found between the lung weights and volumes in all groups (r = 0.1, P > 0.05).
Conclusion: Only TRH alone treatment produced a significant increase in both fetal lung volume and weight compared to the control group. Administering TRH alone can lead to increased lung maturation. Combining TRH to corticosteroid treatment significantly decreased mean fetal lung weight, instead of an increase. According to these results combined used of these two substances probably counteract each others effect, instead of having a synergism.