Protection against adrenochrome-induced myocardial damage by various pharmacological interventions

Perfusion of the isolated rat heart with Krebs-Henseleit solution containing adrenochrome (25 or 50 mg/l), and oxidation product of catechalmines, resulted in contractile failure and myocardial necrosis. Various pharmacological agents known to protect the myocardium against catecholamine-induced necrosis were also found to be effective against adrenochrome-induced changes in the ultrastructure of the isolated perfused rat heart. The alpha-receptor-blocking drugs tolazoline and Dibenamine (dibenzylchlorethamine), and the adrenergic neurone-blocking agents guanethidine and bretylium did not alter the development of contractile failure and necrosis due to adrenochrome. The beta-receptor-blocking compounds propranolol and practolol effectively protected the heart from adrenochrome-induced necrotic damage, and partially prevented contractile failure. The hydrazine-type monoamine oxidase inhibitor iproniazid completely prevented ultrastructural damage and partially maintained contractile-force development in adrenochrome perfused hearts. The non-hydrazine-type monoamine oxidase inhibitor tranylcypromine partially protected the isolated rat heart against adrenochrome necrosis, but disruption of mitochondrial structure was still seen. Tranylcypromine did not significantly improve contractile force development during adrenochrome perfusion. The calcium antagonist D-600 reduced the severity of adrenochrome-induced ultrastructural damage. These results provide strong support for the view that catecholamine-induced cardiotoxicity is mediated through the formation of adrenochrome.