Effects of ovine prolactin on iodide metabolism and thyroid activity in the eel |
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Authors: | A de Luze J Leloup M Olivereau |
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Institution: | (1) Laboratoire de Physiologie générale et comparée du Muséum et Laboratoire d'Endocrinologie comparée, associé au C.N.R.S., 7 rue Cuvier, F-75005 Paris, France;(2) Laboratoire de Physiologie, Institut Océanographique, 195, rue Saint-Jacques, F-75005 Paris, France |
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Abstract: | Summary In the eel, ovine prolactin (oPrl) treatment (0.018 IU/day·g body weight), for 8 to 13 days modifies neither iodide absorption from the water nor excretion, extrathyroidal metabolism and plasma level of iodide.Thyroid activity, evaluated by epithelial cell height, radioiodine uptake and absolute iodide uptake is approximately twice that of controls. However, the amounts of total iodine, thyroxine (T4) and triiodothyronine (T3) in thyroid are unaltered by oPrl. Therefore, the decrease of plasma T4 and the increase of plasma T3, previously observed in oPrl-treated eels, do not result from a preferential thyroidal secretion of T3, but only from a stimulation of peripheral conversion of T4 to T3. Furthermore, the increased thyroid activity probably originates from a decreased feedback inhibition following the fall of circulating T4 induced by oPrl.Abbreviations
oPrl
ovine prolactin
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T
4
Thyroxine
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T
3
3.5.3 triiodothyronine
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TRH
thyrotropin releasing hormone
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TSH
thyroid stimulating hormone
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PBI
protein bound iodine |
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