Effects of betamethasone and thyroid hormone on fetal rat lung maturation in vivo.

We studied the effect of maternal administration at various intervals of betamethasone, triiodothyronine (T3), or both, on fetal rat lung maturation. T3 alone did not enhance choline incorporation to phosphatidylcholine by 20-day fetal lung explants, or morphometric lung maturation. Betamethasone, and betamethasone plus T3, increased both of those parameters over control and T3 values. However, addition of T3 offered no advantage over administration of betamethasone alone. Significant enhancement of morphometric lung maturation was already present after only 24 h of exposure to beta-methasone, or to the combination of hormones. However, choline incorporation to phosphatidylcholine only increased significantly by 36 h of exposure to betamethasone with or without T3.