efeito do t reinamento Físico em Alterações Induzidas pelo envelhecimento no músculo Papilar do rato Effect of Exercise Training on Aging-induced Changes in Rat Papillary Muscle

Summary Background: The effects of aging on papillary muscle have been widely demonstrated, but no data on the effects of exercise on the age-related changes are available. Objective: To analyze the effects of aging on the morphological and quantitative properties of papillary muscle and investigate whether a longterm moderate exercise program would exert a protective effect against the effects of aging. Methods: We used electron microscopy to study the density of myocytes, capillaries and connective tissue and the cross-sectional area of myocytes of the papillary muscle of the left ventricle of 6- and 13-month-old untrained and exercised Wistar rats. Results: As expected, the volume density of myocytes declined significantly (p<0.05) with aging. The length density of myocardial capillaries also declined with aging, but not significantly. The interstitial volume fraction of the papillary muscle tissue increased significantly (P<0.05) with age. The number of myocyte profiles showed a reduction of 20% that was accompanied by myocyte hypertrophy in the aged rats (P<0.05). Animals submitted to a 60-minute daily session,, 5 days/wk at 1.8 km.h -1 of moderate running on a treadmill for 28 weeks showed a reversion of all the observed aging effects on papillary muscle. Conclusion: The present study supports the concept that long–term exercise training restrains the aging-related deleterious changes in the papillary muscle. (Arq Bras Cardiol 2009;92(5):356-360