Integration of cardiac energetics, function and histology from isolated rat hearts perfused with doxorubicin and doxorubicin-ol; a model for use in drug safety evaluations

Abstract

The isolated rat heart (Langendorff) assay combined with NMR spectroscopy and histology were used to elucidate functional, metabolic, and histological signs of cardiotoxicity resulting from acute exposure to clinically relevant concentrations of doxorubicin and its metabolite dox-ol. Doxorubicin blood concentrations and pharmacokinetic parameters were assessed following a clinically relevant dose of 2 mg/kg in order to select concentrations for isolated heart perfusions. Isolated rat hearts were exposed to 1 or 10 μM of doxorubicin or 0.3 μM dox-ol for at least 60 min using the Langendorff perfusion method. Effects on heart function were monitored using ECGs, left ventricular contraction parameters, and microscopic histology. Cardiac energetics (PCr, ATP, and P_i) were evaluated before, during, and after exposure to doxorubicin/dox-ol in perfused hearts using NMR spectroscopy. Cardiac effects were evident following clinically relevant concentrations of doxorubicin and dox-ol in isolated rat hearts demonstrated by altered heart function, energetic reserve, and microscopic lesions. A cardiac stress test utilizing isoproterenol resulted in enhanced functional response and reductions in PCr in doxorubicin versus vehicle treated hearts indicating possible alterations in the isoproterenol mediated pathway. Dox-ol treated hearts were similar to control with regard to function, but exhibited histologic findings. The use of combined Langendorff/NMR/histology methodologies allowed for comparison of multiple indices of cardiac function at one time in which cardiac effects were evident in multiple parameters. SHORT ABSTRACT: The isolated rat heart assay combined with NMR spectroscopy and histology was used to elucidate functional, metabolic, and histological signs of cardiotoxicity resulting from acute exposure to clinically relevant concentrations of doxorubicin and its metabolite dox-ol. Heart function was altered and microscopic signs of toxicity were evident with dox and dox-ol exposures. The use of combined Langendorff/NMR/histology assays allowed for comparison of multiple indices of cardiac function at one time in which cardiac effects were evident in multiple parameters.

Keywords: ATP; Cardiotoxicity; Doxorubicin; Doxorubicin-ol; Heart function; Histology; Isolated heart; NMR; Phosphocreatine.