Heart infarction-like effect induced by natural catecholamines in vitro

Isolated rat hearts were perfused using retrograde technique under constant perfusion pressure or under constant coronary flow. The addition of L-epinephrine or L-nor-epinephrine (1 microgram per ml) into the perfusion medium for one hour caused visible and irreversible morphological changes. They became apparent usually after 4 hours of perfusion in the form of small, pale, opaque spots of streaks gradually enlarging on the surface or on the transverse section of myocardium. Light microscope and electron microscope examination showed the disintegration process analogous to myocardial infarction but lacking the infiltration with blood elements. The structural changes were preceeded by increased release of lactate dehydrogenase into the effluent, the most characteristic metabolic change a accompanying myocardial injury. Although the underlying mechanism of cardiotoxic action catecholamines remains to be clarified, several factors under consideration could be eliminated like hyperlipidemia, thrombogenic process or reduced total coronary inflow rate.