Acute myocardial histopathology in normal and arteriosclerotic rats during isoproterenol-induced infarction

Abstract

Arteriosclerotic and non-arteriosclerotic, male Sprague-Dawley rats were given 2 s.c. injections of isoproterenol known to produce extensive myocardial infarction. The appearance of positive fuchsinophilia was used as an index of focal myocardial acidosis and of anaerobic metabolism. After one injection of isoproterenol, positive fuchsinophilia appeared within 30 min., reached a zenith at 4 hr and then promptly disappeared. Following the second injection of isoproterenol, fuchsinophilia reappeared briefly but was not as intense. The arteriosclerotic animals showed markedly less evidence of heart failure outwardly and less evidence of fuchsinophilia, histopathologically. Apparently, the first episode of cardiac stimulation caused only temporary cardiac ischaemia, positive fuchsinophilia and anaerobic cardiac metabolism. After the second injection, however, irreversible cardiac damage occurred and despite an abortive attempt towards anaerobic metabolic readjustment overt cardiac necrosis became dominant.