Gestation-related and betamethasone-induced changes in 11β-hydroxysteroid dehydrogenase types 1 and 2 in the baboon placenta

OBJECTIVE: We determined developmental and labor-related changes in 11β-hydroxysteroid (HSD) 1 and 2 expression in baboon placentas during the final third of gestation and labor. We examined whether maternal glucocorticoid administration alters placental 11β-HSD 2 expression. STUDY DESIGN: Maternal and fetal plasma cortisol concentrations were measured in five animals. Types 1 and 2 11β-HSD messenger RNA (mRNA) and protein in placentas obtained at 121 to 185 days' gestation (dGA, term approximately 185 dGA, n = 16), during labor between 141 and 193 dGA (n = 8), and after maternal administration of four doses of 87.5 μg/kg betamethasone (n = 5) at 12-hour intervals at 121 to 135 dGA were analyzed by Northern and Western blot. RESULTS: Cortisol levels were higher in maternal plasma than fetal (4-fold, P < .00001). Placental 11β-HSD 2 mRNA and protein decreased after 0.9 gestation (P < .001). 11β-HSD 1 mRNA remained unchanged. There was no effect of labor on placental 11β-HSD 1 and 2 mRNA and protein levels. Maternal betamethasone administration dramatically increased (P < .05) 11β-HSD 2 mRNA as well as protein without effect on 11β-HSD 1 mRNA and protein expression. CONCLUSIONS: The late-gestation baboon maternal plasma cortisol concentration is four times the fetal plasma concentration. Decreased placental 11β-HSD 2 may enhance maternal cortisol passage to the fetus at the end of gestation, thereby contributing to cortisol-mediated changes within the placenta and cortisol in fetal plasma at this stage of fetal development. The positive effect of betamethasone on placental 11β-HSD 2 induction further suggests an ability of the placenta to regulate glucocorticoid transfer in the presence of elevated maternal glucocorticoid.