Triiodothyronamine--a beta-adrenergic metabolite of triiodothyronine?
Triiodothyronamine (Triam) is a potential metabolite of triidothyronine (T3), resulting from decarboxylation of the side-chain. In an attempt to elucidate the physiological properties of Triam we have investigated the binding of Triam to beta-adrenergic receptors, using turkey-erythrocytes and performing binding studies with ( (-)(3H)-dihydroalprenolol) ( (-)(3H)-DHA) as a specific beta-adrenergic ligand. The inhibition constant Ki for Triam was determined as 5 X 10(-6) M, compared to dopamine (Ki = 1,3 X 10(-2) M), norepinephrine (Ki = 3 X 10(-4) M), epinephrine (Ki = 5 X 10(-5) M) and isoproterenol (Ki = 3 X 10(-6) M). The inhibition of ( (-)(3H)-DHA)-binding by Triam was further compared with other iodothyronines thyroxine (T4), T3, 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine (3,3'-T2). It is concluded that Triam binds to beta-adrenergic receptors like naturally occurring amines but different from typical circulating iodothyronines.
D000818:Animals; D003653:Decarboxylation; D004082:Dihydroalprenolol / Q000378:metabolism; D004104:Diiodothyronines / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000031:analogs & derivatives* / Q000378:metabolism*; D014285:Triiodothyronine, Reverse / Q000378:metabolism; D014422:Turkeys
D004104:Diiodothyronines; D011943:Receptors, Adrenergic, beta; D014284:Triiodothyronine; C040407:3,3',5-triiodothyronamine; D014285:Triiodothyronine, Reverse; D004082:Dihydroalprenolol; D007545:Isoproterenol; D013974:Thyroxine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine