Avaliação da função mecânica dos músculos papilares e do remodelamento cardíaco de ratos idosos submetidos ao treinamento físico aeróbico

Abstract

Aging awakens progressive deterioration of function of different organ systems, where there is a gradual process of structural remodeling, cellular and molecular levels. Thus, it seems reasonable to accept that measures interrupting or slowing of inotropic myocardial depression are highly recommended. In this scenario, there is information available that allow us to consider exercise as pharmacological tool highly recommended. Thus, the purpose of this study was to evaluate the role of physical exercise performed in a pool under the depression of myocardial contractility associated with aging. We used 39 male rats with 24 months (aged) Wistar divided into two groups, the trained (n = 25) and sedentary (n = 14). The training protocol consisted of swimming in a heated pool for 6 weeks, being the first week an adaptation period. Animals in the trained group were subjected to training 1h30min/dia, 6 days/week. After the training period, animals were sacrificed and the heart was weighed and dissected for analysis of the mechanical action of the papillary muscles contracting isometrically heart. Functional variables were determined at optimum length - Lmax, developed tension (DT), resting tension (RT), maximum rate of change of developed tension positive (+ dT/dt) and negative (-dT/dt), time to achieve peak tension (TPT) and time to the tension developed to decrease 50% of its maximum value (TR50%). Aged animals showed significant cardiac hypertrophy trained bi-ventricular functional capacity, improvement of myocardial inotropism, force generation and relaxation, and reduction of collagen content and increased nuclear volume of cardiomyocytes. Based on these results, we conclude that exercise training induced enhancement of mechanical function and cardiac remodeling in aged rats subjected to physical training.