Effect of amiodarone on myosin isoenzymic distribution in rat ventricular myocardium

Abstract

Rats were given amiodarone (50 mg X kg-1 X day-1, orally) for 4 weeks and the distribution of ventricular isomyosins, a sensitive index of the effects of thyroid hormones on cardiac tissue, was analyzed. Amiodarone treatment induced a marked increase in both T4 and rT3 and tended to decrease T3 serum levels. At the pharmacologically active dosage we used, the drug induced a moderate redistribution of ventricular isomyosins in favour of V, at the expense of V1. Our results do not support the hypothesis that the major mechanism of action of amiodarone is mediated through hypothyroid-like effects.