Hypothyroid-like effect of amiodarone in the ventricular myocardium of the rat

Publisher Website
Google Scholar
Abstract
Due to the similar electrophysiological effects of amiodarone and hypothyroidism in the myocardium, the induction of a local hypothyroid state has been proposed as the mechanism of action of amiodarone. To examine this hypothesis we have studied the influence of amiodarone on the distribution of ventricular isomyosins — a sensitive parameter of the thyroid state in the rat heart — and the effects of amiodarone on 3,5,3′-triiodothyronine (T3) myocardial nuclear receptor binding in vivo. Amiodarone induced a dosage-dependent redistribution of isomyosins similar to hypothyroidism, while simultaneously inducing a low T3 syndrome at the higher dose level. In hypothyroid rats, which were pretreated with amiodarone, substitution of T3 (2 μg/100 g) led to a complete reversal of the myosin pattern not differing from control hypothyroid rats which were only given T3; the effect of T3 (0.5 μg/100 g) was however partially inhibited by amiodarone. Nuclear receptor binding of T3 determined in hypothyroid rats in vivo was unaffected by amiodarone. We conclude that amiodarone induces a hypothyroid-like state in the ventricular myocardium of rats by inhibiting the action of T3 — an effect which cannot be attributed to an antagonism at the T3 nuclear receptor level.

This publication has 21 references indexed in Scilit: