This study was performed to determine the effects of 8 weeks testosterone enanthate (TE) injection and resistance training (RT) on cardiac muscle in male Wistar rats. 28 male adult Wistar rats were randomly divided into 4 groups; control + placebo, RT + placebo, TE and TE+RT. Testosterone enanthate (20mg.kg-1 BW, IM) and placebo (olive oil; 0.2 mL, IM) were injected twice a week for two months. The RT consisted of climbing (5 reps/3 sets) a ladder carrying a load suspended from the tail. The serum activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and creatine kinase MB (CK-MB) and serum level of creatinine, urea and cardiac troponin I (CTnI) were evaluated. After sacrifice, samples from myocardial muscle were collected for histopathology evaluation. The serum concentration of CTnI and CK-MB activity significantly increased in group RT compared with control (p<0.05). In group RT+TE, all biomarkers of muscle damage (CTnI, CK-MB, AST, LDH) were significantly more than those in control (p<0.05). Also mild myocardial hypertrophy was observed in RT and RT+TE groups. The higher level of all heart damage biomarkers in the RT+TE group rather than control may indicates the synergistic effects of medication and exercise. Key words: Anabolic androgenic steroids, Doping, Exercise, Heart

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