Activation of the @entity2339 of fetal @entity742 during late gestation is associated with increases in plasma concentrations of adrenocorticotropic hormone (ACTH) and @entity701 , and ultimately results in parturition. However, the mechanisms contributing to the concurrent increases in ACTH and @entity701 are unclear. Plasma @entity53 -17 beta (E2) concentrations increase progressively in the prepartum ovine fetus, and we hypothesized that E2 may influence HPA activity by affecting either basal and/or @entity519 -stimulated ACTH release. We examined potential mechanisms, including altered expression of pro-opiomelanocortin (POMC) in fetal pituitary corticotrophs, and changes in corticosteroid binding globulin (CBG) and/or the enzymes 11 beta @entity14128 dehydrogenase (11 beta HSD)-1 or 11 beta HSD-2 in liver and placenta, that could alter negative feedback control. We infused fetal @entity742 at 127 d of gestation with either E2 (100 micrograms/24 h) or saline for 100 h. Fetal arterial blood samples were collected at 8 h intervals during the infusion of E2 or saline (n = 4), for measurement of basal plasma ACTH and @entity701 concentrations, as well as plasma corticosteroid binding capacity (CBC). Placenta and fetal liver samples were collected at 100 h for measurement of placental @entity70321 and 11 beta HSD-2 mRNA and hepatic CBG and @entity70321 mRNA, by Northern blotting. Fetal pituitary samples were collected for measurement of POMC mRNA by in situ hybridization. In a separate experiment, fetuses were exposed to 2 h of @entity519 at 75 h of E2 or saline infusion (n = 4), and fetal arterial blood samples were collected during the period of @entity519 for measurement of plasma ACTH and @entity701 concentrations. E2 infusion had no effect on basal plasma concentrations of ACTH or total @entity701 , or on the stimulated levels of ACTH or total @entity701 achieved in response to @entity519 . Basal fetal pituitary POMC mRNA also did not change significantly with E2 infusion. No significant increases were observed in plasma CBC during E2 administration. However, hepatic CBG and @entity70321 mRNA were significantly elevated in the livers of E2-treated fetuses. Placental @entity70321 mRNA; but not 11 beta HSD-2 mRNA was increased by E2 treatment. These data do not support a direct effect of exogenous E2 at the level of basal or @entity519 -stimulated ACTH output, but suggest that elevated E2 concentrations may alter the expression of genes encoding proteins implicated in tonic regulation of fetal HPA function.

The effects of XXXX -17 beta infusion into fetal @entity742 in late gestation.

@entity70321 :: ('443409(Tax:9940)', 'Gene') :: ['11 beta HSD-1'] @entity742 :: ('9940', 'Species') :: ['sheep'] @entity14128 :: ('CHEBI:35350', 'Chemical') :: ['hydroxy steroid'] @entity53 :: ('MESH:D004958', 'Chemical') :: ['estradiol'] @entity519 :: ('MESH:D000860', 'Disease') :: ['hypoxemia'] @entity2339 :: ('MESH:D007029', 'Disease') :: ['hypothalamic-pituitary-adrenal (HPA) axis'] @entity701 :: ('MESH:D006854', 'Chemical') :: ['cortisol']
@entity53 :: (MESH:D004958,Chemical) :: ['estradiol']
