Experiences with isoprenaline induced myocardial necrosis in the rat

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Abstract
Myocardial lesions produced in the rat by isoprenaline were quantified for use as a model to assess possible incremental effects of environmental and dietary factors. This was initially made difficult by variation in the cardiotoxicity of different samples of isoprenaline. Investigation of these samples failed to reveal the basis for the differences. Active preparations produced profound changes both clinically and pathologically. The earliest light microscopic change was loss of fuchsinophilia of fibers in sections stained by the picro-Mallory technique. By 24 h obvious necrosis, fragmentation and lysis of the fibers occurred. Treatment of frozen sections to demonstrate succinate dehydrogenase showed early changes in the character of formazan, suggesting the possibility of a transient alteration in the H transport system. By 48 h, this was reversed except in those fibers undergoing necrosis where there was a complete loss of formazan. This contrast in staining between normal and necrotic fibers constituted the basis for quantification which was carried out by point counting. Some differences were seen in the amount of myocardial necrosis between different batches of animals but relatively small differences within individual batches, suggesting that the introduction of additional variants into the system should be capable of producing clear cut results.