title: Effects of catecholamines on plasma thyroid hormone levels in arctic charr, Salvelinus alpinus.
abstract: Plasma levels of L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) were measured in arctic charr at 2, 6, or 24 hr after single intraperitoneal injection of epinephrine (E) or norepinephrine (NE). At a dose of approximately 1 microgram/g body wt (sufficient to cause a submaximal dermal melanophore pallor response) plasma T4 was usually elevated at 2 hr, consistently depressed at 6 hr, and unaffected at 24 hr. There was no effect of E on plasma [125I]T4 kinetics or [125I]T4 5'-monodeiodination to [125I]T3. Plasma T3 showed no consistent response to E or NE at any sampling time. At an E dose of 4 ng/g body wt (probably sufficient to cause a physiological elevation in plasma E level), neither plasma T4 nor T3 levels were altered at 6 hr. Acute depression in plasma T4 by the high doses of E and NE may reflect a local neurotransmitter role of catecholamines in inhibiting thyroidal T4 release through action at thyroidal, hypophysial, or hypothalamic levels.
mesh_terms: D000818:Animals; D001110:Arctic Regions; D004837:Epinephrine / Q000494:pharmacology*; D007700:Kinetics; D009638:Norepinephrine / Q000494:pharmacology*; D012487:Salmonidae / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D014337:Trout / Q000097:blood*
chemical_list: D014284:Triiodothyronine; D013974:Thyroxine; D009638:Norepinephrine; D004837:Epinephrine