Exercise Training Prevents β-Adrenergic Hyperactivity-Induced Myocardial Hypertrophy and Lesions

BACKGROUND: Sustained beta-adrenoreceptor activation promotes cardiac hypertrophy and cellular injury. AIMS: To evaluate the cardioprotective effect of exercise on damage induced by beta-adrenergic hyperactivity. METHODS: Male Wistar rats were randomised into four groups (n=8 per group): sedentary non-treated control (C), sedentary treated with isoproterenol 0.3 mg/kg/day administered subcutaneously for 8 days (I), exercised non-treated (E) and exercised plus isoproterenol administered during the last eight days of exercise (IE). Exercised animals ran on a treadmill for 1 h daily 6 times a week for 13 weeks. RESULTS: Isoproterenol caused increases in left ventricle (LV) wet and dry weight/body weight ratio, LV water content and cardiomyocyte transverse diameter. Additionally, isoproterenol induced severe cellular lesions, necrosis, and apoptosis, increased collagen content and reduced capillary and fibre fractional areas. Notably, all of these abnormalities were completely prevented by exercise. CONCLUSION: Our data have demonstrated that complete cardioprotection is possible through exercise training; by preventing beta-adrenergic hyperactivity-induced cardiac hypertrophy and structural injury.