Beta-adrenergic ligand binding to rat cardiac membranes following amiodarone administration

The effects of chronic administration of the anti-arrhythmic drug amiodarone on the beta-adrenergic receptors of rat myocardium were investigated using ³H-dihydroalprenolol to directly measure the density of binding sites on crude membrane preparations. Amiodarone hydrochloride was given intraperitoneally at a dosage of 10 mg/kg daily for 3, 7 or 14 consecutive days to adult male rats. 24 hours following the last dose the animals were sacrificed and ventricular membranes prepared for ligand binding measurements. Specific binding was determined in the presence of propranolol, and binding data were analyzed by a Scatchard plot to yield the density and affinity of binding sites. Data from treated groups were compared to appropriate controls by unpaired Student's t-test. No significant differences in either density or affinity of sites were found for any of the periods of drug treatment. It is concluded that the anti-arrhythmic actions of amiodarone do not involve changes in myocardial beta-adrenergic responsiveness at the level of receptor recognition sites.