title: Dronerarone acts as a selective inhibitor of 3,5,3'-triiodothyronine binding to thyroid hormone receptor-alpha1: in vitro and in vivo evidence.
abstract: Dronedarone (Dron), without iodine, was developed as an alternative to the iodine-containing antiarrhythmic drug amiodarone (AM). AM acts, via its major metabolite desethylamiodarone, in vitro and in vivo as a thyroid hormone receptor alpha(1) (TRalpha(1)) and TRbeta(1) antagonist. Here we investigate whether Dron and/or its metabolite debutyldronedarone inhibit T(3) binding to TRalpha(1) and TRbeta(1) in vitro and whether dronedarone behaves similarly to amiodarone in vivo. In vitro, Dron had a inhibitory effect of 14% on the binding of T(3) to TRalpha(1), but not on TRbeta(1). Desethylamiodarone inhibited T(3) binding to TRalpha(1) and TRbeta(1) equally. Debutyldronedarone inhibited T(3) binding to TRalpha(1) by 77%, but to TRbeta(1) by only 25%. In vivo, AM increased plasma TSH and rT(3), and decreased T(3). Dron decreased T(4) and T(3), rT(3) did not change, and TSH fell slightly. Plasma total cholesterol was increased by AM, but remained unchanged in Dron-treated animals. TRbeta(1)-dependent liver low density lipoprotein receptor protein and type 1 deiodinase activities decreased in AM-treated, but not in Dron-treated, animals. TRalpha(1)-mediated lengthening of the QTc interval was present in both AM- and Dron-treated animals. The in vitro and in vivo findings suggest that dronedarone via its metabolite debutyldronedarone acts as a TRalpha(1)-selective inhibitor.
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands. h.c.vanbeeren@am.uva.nl
authors.forename: H C
authors.initials: HC
authors.lastname: Van Beeren
authors.forename: W M C
authors.initials: WM
authors.lastname: Jong
authors.forename: E
authors.initials: E
authors.lastname: Kaptein
authors.forename: T J
authors.initials: TJ
authors.lastname: Visser
authors.forename: O
authors.initials: O
authors.lastname: Bakker
authors.forename: W M
authors.initials: WM
authors.lastname: Wiersinga
mesh_terms: D000638:Amiodarone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000737:chemistry / Q000494:pharmacology; D000077764:Dronedarone; D004789:Enzyme Activation / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007453:Iodide Peroxidase / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D037021:Thyroid Hormone Receptors alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
chemical_list: D000889:Anti-Arrhythmia Agents; D037021:Thyroid Hormone Receptors alpha; D014284:Triiodothyronine; D007453:Iodide Peroxidase; D000077764:Dronedarone; C036116:desethylamiodarone; D000638:Amiodarone