Antibiotics, Antineoplastic/toxicity; Apoptosis/drug effects; Cardiomyopathies/prevention & control; Cardiovascular Agents/therapeutic use; Doxorubicin/toxicity; Myoblasts/drug effects; Thrombopoietin/therapeutic use; Animals; Antibiotics, Antineoplastic/pharmacology; Blood Cell Count; Cardiomyopathies/chemically induced; Cardiomyopathies/diagnostic imaging; Cardiomyopathies/pathology; Cardiovascular Agents/pharmacology; Cells, Cultured/drug effects; Cells, Cultured/ultrastructure; Doxorubicin/pharmacology; Drug Evaluation, Preclinical; Heart Rate/drug effects; Male; Mice; Mice, Inbred BALB C; Myoblasts/ultrastructure; Myocytes, Cardiac/drug effects; Myocytes, Cardiac/ultrastructure; Proto-Oncogene Proteins c-akt/physiology; Rats; Razoxane/pharmacology; Razoxane/therapeutic use; Reactive Oxygen Species/metabolism; Single-Blind Method; Thrombopoietin/pharmacology; Ultrasonography