Mitigation of an anthracycline-induced cardiomyopathy by pretreatment with razoxane: a quantitative morphological assessment.

A quantitative evaluation of structural modifications was undertaken in the myocardium of daunorubicin (DNR)-treated and razoxane (RZ)-protected mice. BDF1 mice were injected with DNR, 15 mg/kg; a second group of mice was subjected to the same conditions but, in addition, received a pretreatment of RZ, 200 mg/kg. Representative cubes of myocardial tissue were processed for viewing with the electron microscope. Five hundred myocardial cells in each group were examined for the presence of lesions which had been categorized as early, moderate, or advanced. Contrasting the total number of demonstrable lesions in each group revealed a statistically significant reduction of 38% in abnormalities present in RZ-protected mice. By category, RZ-pretreated mice showed a mitigation in the appearance of early and moderate alterations and a striking reduction in the incidence of advanced, irreversible lesions. These results indicate that the cardiomyopathy associated with DNR administration can be ameliorated by pretreatment with RZ; this protective effect is markedly exerted by preventing the development of severe, irreversible lesions in the murine myocardium; the initial, non-transient structural alteration subsequent to DNR-exposure appears to affect the myocardial sarcoplasmic reticulum.