Effects of Maternal Administration of Dexamethasone and Thyrotropin-Releasing Hormone on Fetal Rat Pulmonary Surfactant Synthesis

Abstract

To determine the effects of maternal administration of dexamethasone (DEX) and thyrotropin-releasing hormone (TRH) on fetal lung maturation, 16 pregnant rats were divided into the following four groups: 20 μg/kg TRH twice a day was given intraperitoneally to the TRH group rats, 0.5 mg/kg/day DEX to the DEX group and both DEX and TRH to the DEX + TRH group for 3 consecutive days from gestational day 17. The control rats were given an equivalent volume of saline. The pregnant rats were sacrificed on gestational day 20 and the fetal lungs were removed. The relative amounts of surfactant protein A (SP-A), B (SP-B) and C (SP-C) mRNAs were analyzed by Northern blotting and the total lung disaturated phosphatidylcholine (DSPC) contents were determined using an enzymatic method. The SP-B and -C mRNA and DSPC contents in the DEX and DEX + TRH groups were significantly higher than those in the control group, whereas the SP-A mRNA levels did not differ significantly among the four groups. The SP-B and -C mRNA and DSPC contents in the DEX and DEX + TRH groups did not differ significantly. These findings suggest that TRH has no effects on the regulation of surfactant protein mRNAs or DSPC contents in the fetal rat lung and has no additive effects when combined with DEX.

The lungs in congenital diaphragmatic hernia: Do we understand?

“…59,60,69,73,74 In humans and several animal species the combined administration of glucocorticoids and thyroid hormones has a synergistic effect on surfactant synthesis but not on the regulation of surfactant proteins or the amount of saturated PC. 59,60,69,75 Several studies indicate that the possible synergistic effects of glucocorticoids and thyroid hormones on surfactant synthesis coincides with depressed AOE activity at birth and inadequate protection against O 2 free radicals. 73,74 In clinical trials glucocorticoids have a positive effect on the incidence of respiratory distress syndrome and the mortality rate of prematurely born infants, 67 although the addition of TRH to glucocorticoids was associated with maternal and perinatal risks.…”