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Thyroid Hormone Replacement Restores Circulating Enkephalin Concentrations in Hypophysectomized Fetal Sheep
Author(s) -
Simonetta Giuseppe,
Young I. Ross,
McMillen I. Caroline
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.63041386.x
Subject(s) - endocrinology , medicine , gestation , fetus , saline , hypophysectomy , hormone , chemistry , thyroid , biology , pregnancy , genetics
We have investigated the effects of fetal hypophysectomy (HX) with or without thyroxine (T 4 ) 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 + T 4 (0.61 ± 0.08 pmol/L) groups. During the first 15 days of the T 4 or saline infusion, the plasma concentrations of free Met‐Enk were significantly higher in the HX + T 4 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 + T 4 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.