fluorescence spectra of cardiac myosin and in vivo experiment: studies on daunorubicin-induced cardiotoxicity

objective(s):the objective of this study was to investigate the interaction of daunorubicin (dnr) and cardiac myosin (cm) and the changes in mice hearts to exhibit dnr-induced cardiotoxicity . materials and methods:the interaction between dnr and cm was expressed using fluorescence quenching at ph 4.0-9.0 and 15-37 °c. dnr-induced cardiotoxicity was studied using in vivo experiment.  forty groups mice were used control group in which mice were treated with dnr orally, and three dnr-treated groups in which mice were injected intraperitoneally with dnr at seven bolus doses of 2.0, 4.0, and 6.0 mg/kg body weight, respectively. heart indices and myocardial enzyme levels were obtained by histopathological and biochemical analysis. results:the fluorescence quenching mechanism of dnr-cm complex was observed to be a static procedure at 20 °c (ph 7.4), and weakly acidic environment (ph 4.0-6.0) or higher temperature(30-37 °c) promoted the interaction between dnr and cm, causing variations in conformation and normal physiological functions of cm. thermodynamic studies demonstrated that the binding of dnr to cm was a spontaneous process driven by entropy. it also indicated that hydrophobic interaction and hydrogen bonds may play essential roles in the combination of dnr with cm. in addition, 4.0-6.0 mg/kg dnr-treated mice exhibited obvious histopathological lesion, increase in myocardial enzyme level, and reductions in blood cell count. conclusion:our results are valuable for better understanding the particular mode of dnr-cm interaction, and are important to have a deeper insight into the dnr-induced cardiotoxicity.