RESUMO
Aging is characterized by impaired contractile function in the heart. Meanwhile, during senescence the heart faces a high risk of free radical injury which may be a reason for development of myocardial dysfunction in the aged heart. To investigate this, we compared the effects of swim exercise training versus vitamin E treatment on age associated changes in intrinsic cardiac function in response to beta- adrenergic stimulation, induced ischemia and reperfusion. Rats were divided into a] control group b] exercise-trained group c] vitamin E treated group. Isolated hearts were studied in a Langendorff preparation for their intrinsic properties, and their responses to beta- adrenergic stimulation. After recovery the isolated hearts were subjected to global ischemia followed by reperfusion. The results showed that the exercise program adopted resulted in enhancement of time to peak tension response of aged hearts to beta- adrenergic stimulation. Following ischemia/reperfusion [I/R], such program enhanced half relaxation time. Treatment of the aged hearts with vitamin E maintained coronary blood flow and improved the inotropic cardiac reserves. Vitamin E proved to be cardioprotective against the toxic doses of catecholamines as well as the injury of post I/R on the heart. Coronary effluent from hearts of vitamin E _ treated rats had the significant highest level of nitrate compared to the other two groups when measured at 3.46 micro g dose of isoproterenol and at 30 min of reperfusion. Vitamin E enhanced cardiac responsiveness to beta- adrenergic stimulation, and protected the aged heart against I/R injury. Preservation of NO from being transformed to peroxynitrite by antioxidant action of vitamin E may have played a significant role. Swim- training program did not show promising cardio-protective effects against cardiac changes associated with the aging process