Recovery response of melatonin in induced myocardial infarction in adult male rabbits

الملخص EN

Because myocardial infarction (MI) is a major cause of morbidity and mortality worldwide, protecting and remedy of the heart from the ischemia is the focus of intense research.

This study aims to investigate the effects and the possible mechanism of melatonin in isoproterenol (ISO) induced acute MI in rabbits by studying electrocardiography (ECG), its angiogenic role, anti-inflammatory and antioxidants effects as well as histopathological changes of the cardiac muscle.

Materials and Methods: A total of 50 rabbits were randomly divided into 5 groups , each of which were 10 rabbits: (I) Control group: received vehicle only, (II) Melatonin group: received melatonin in a dose of 10 mg/kg by intraperitoneal injec on (i.p), (III) MI group: MI was induced with ISO (85 mg /kg) administered subcutaneously twice at an interval of 24 h.

(IV) Prophylac c group: melatonin injec on was done for 7 days and induc on of infarc on with ISO was done at the 6th and 7th day of the experiment and (V) Therapeutic group: injected with ISO in the 1st and 2nd day and melatonin was given for 7 days star ng at day one of induced infarc on.

The following parameters were evaluated: ECG, heart weight/ body weight (HW/BW) ratio, serum levels of cardiac marker enzymes [creatinine kinase-MB (CK-MB), lactate dehydrogenase (LDH) and cardiac troponin-T (cTnT)]., inflammatory markers [serum tumor necrosis factor-α (TNFα) and cardiac myloperoxidase (MPO) enzyme], cardiac total peroxides level, total antioxidant capacity (TAC), oxidative stress index (OSI), angiogenic markers [cardiac vascular endothelial growth factor (VEGF) and inducible nitric oxide (iNO)], and histopathological changes of the cardiac muscle.

Results: ISO induced MI rabbits showed significant pathological changes in the ECG pattern (elevated ST-segment and decreased R amplitude), significant increased HW/BW ratio, significant increased serum levels of cardiac marker enzymes (CK-MB, LDH and cTnT).

Also, inflammatory markers (serum TNF-α and cardiac MPO), angiogenic markers (VEGF and iNO), total peroxides and OSI were significantly higher whereas TAC were significantly lower in MI group as compared to control group.

The histopathological findings of the myocardial tissue evidenced myocardial damage in ISO induced MI rabbits.

Administration of melatonin in prophylactic and therapeutic groups revealed that melatonin has an efficient anti-inflammatory and antioxidant activity, reduced the cardiac marker enzymes and the pathological ECG patterns, ameliorated the increase in the HW/BW ratio and augmented myocardial angiogenesis.

Also, decreased myocardial damage was evidenced by the histopathological findings with melatonin administration.

The mending effects of melatonin in prophylactic group were more prominent than in the therapeutic group.