Quantification of myocardial necrosis and cardiac hypertrophy in isoproterenol-treated rats

Administration of a single high dose or multiple low doses of isoproterenol (ISO) to rats induces myocardial necrosis and cardiac hypertrophy. To assess the extent of necrosis we measured myocardial activities of creatine kinase (CK) and aspartate aminotransferase (AST) in the first days after ISO-treatment. After a single high dose and multiple low doses of ISO, necrosis was 10% and 25%, respectively. To quantify the degree of hypertrophy we measured heart weight and myocyte volume, and calculated cardiac CK, AST and DNA content up to 50 days after ISO-treatment. After a single high dose and multiple low doses of ISO, myocyte volume increased by 27% and 92%, respectively, while heart weight increased by 15% and 56%, respectively. As in this model hypertrophy is associated with focal necrosis, heart weight gain underestimates the actual increase of myocyte volume.