Effects of antenatal betamethasone and dexamethasone on the lung expression of vascular endothelial growth factor and alveolarization in newborn rats exposed to acute hypoxia and recovered in normoxia or hyperoxia.

The use of antenatal corticosteroids is widespread and it is important to know their effect(s) on vascular endothelial growth factor (VEGF), which plays a crucial role in pulmonary development. The purpose of this study was to compare pulmonary VEGF expression in newborn rats that were exposed to antenatal betamethasone versus dexamethasone under normoxia, hypoxia and oxidative stress, and to evaluate its impact on alveolarization. Betamethasone, dexamethasone or equivalent saline solution (control group) was administered to pregnant rats. Newborn rats were randomized to room air, hypoxia followed by hyperoxia, or hypoxia followed by air. Pulmonary VEGF protein, VEGF mRNA, and alveolarization were evaluated at 4 days of life. Betamethasone and dexamethasone were observed to have different actions on VEGF expression with a correlation with alveolarization. Antenatal dexamethasone decreased VEGF expression, and dexamethasone and hyperoxia had an additive effect on the inhibition of VEGF with a reduction in alveolar development. Betamethasone appeared to have an effect on the induction of the expression of VEGF, and it seemed to inhibit the negative action of hyperoxia on VEGF. Moreover, betamethasone did not produce a decrease in alveolarization. Our results support the notion that betamethasone could be better than dexamethasone for antenatal lung maturation.