Thyroid Hormone Replacement Restores Circulating Enkephalin Concentrations in Hypophysectomized Fetal Sheep |
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Authors: | Giuseppe Simonetta I Ross Young I Caroline McMillen |
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Institution: | Department of Physiology, Monash University, Clayton, Victoria, Australia |
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Abstract: | 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. |
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Keywords: | Hypophysectomy Sheep fetus Thyroxine Plasma Free methionine-enkephalin Noradrenaline Adrenaline Gestation Athyroidism |
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