title: Thyroid hormone replacement restores circulating enkephalin concentrations in hypophysectomized fetal sheep.
abstract: We have investigated the effects of fetal hypophysectomy (HX) with or without thyroxine (T4)replacement on the plasma concentrations of free methionine-enkephalin (free Met-Enk), noradrenaline, and adrenaline in late gestation sheep fetus. Plasma adrenaline concentrations were significantly higher in intact fetal sheep (1.05 +/- 0.12 pmol/L) between 125 and 140 days of gestation when compared with the HX + saline (0.64 +/- 0.10 pmol/L) and HX + T4 (0.61 +/- 0.08 pmol/L) groups. During the first 15 days of the T4 or saline infusion, the plasma concentrations of free Met-Enk were significantly higher in the HX + T4 group (392 +/- 40 pmol/L) than in the HX + saline group (299 +/- 43 pmol/L). At this stage of gestation, however, circulating concentrations of free Met-Enk were significantly higher in intact fetal sheep (556 +/- 51 pmol/L) than in either of the HX groups. Between 125 and 140 days of gestation, plasma free Met-Enk concentrations were similar and significantly higher in the intact and HX + T4 groups than those measured in the HX + saline fetal sheep. We conclude that the decrease in circulating free Met-Enk concentrations after removal of the fetal pituitary is primarily a consequence of functional athyroidism.
authors.affiliation: Department of Physiology, Monash University, Clayton, Victoria, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Simonetta
authors.forename: I R
authors.initials: IR
authors.lastname: Young
authors.forename: I C
authors.initials: IC
authors.lastname: McMillen
mesh_terms: D000818:Animals; D004744:Enkephalin, Methionine / Q000097:blood*; D004837:Epinephrine / Q000097:blood; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D007016:Hypophysectomy; D007262:Infusions, Intravenous; D009638:Norepinephrine / Q000097:blood; D011247:Pregnancy; D012756:Sheep; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*
chemical_list: D004744:Enkephalin, Methionine; D013974:Thyroxine; D009638:Norepinephrine; D004837:Epinephrine