The present study was carried out to investigate whether S-methyl cysteine (SMC) would ameliorate the acute cardiotoxic effect of tilmicosin antibiotic in treated Wister rats. Thirty-two male rats were equally divided into four groups: control, SMC (100 mg/kg orally for five consecutive days), tilmicosin (a single dose, 75 mg/kg BW, S/C on the sixth day) and SMC+Tilmicosin (pretreated with SMC and co-injected with 75 mg/kg of tilmicosin at the sixth day). The biochemical results demonstrated marked increase in serum aspartate transaminase (AST), lactate dehydrogenase (LDH), creatine kinase (CK) activities and cardiac troponin T (cTnT) concentrations in tilmicosin-treated rats indicating severe cardiotoxicity. On the other hand, pretreatment of rats with SMC revealed marked decrease in cardiac biochemical parameters toward the normal limits. Histopathological findings of the heart sections revealed multifocal myocarditis in tilmicosin-treated rats meanwhile, (SMC+Tilmicosin) treated group showed slight vacuolation of myocardial fiber. Furthermore, the ultrastructure findings revealed myolysis and necrosis in tilmicosin-treated rats compared with intact myocardial fiber in (SMC+Tilmicosin) group.

Key words: Cardiotoxicity, Rats, S-methyl cysteine, Tilmicosin