Efeitos de um programa de exercício físico prévio ao infarto do miocárdio sobre a morfologia e a função contrátil do ventrículo esquerdo de ratos / Effects of a physical exercise program previous to myocardial infarction on the left ventricle morphology and contractile function of rats

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

20/08/2010

RESUMO

The aim of this study was to verify the effects of a treadmill running program previous to myocardial infarction (MI) on the myocardium morphology and contractile function of rats. One-month old male Wistar rats were randomly divided into three groups: sedentary infarcted (INF SED, n = 13), exercised infarcted (INF EX, n = 26) and simulated infarction (SHAM, n = 12). Before surgery animals from INF EX were subjected to a program of treadmill running (5 days / week, 1 hour/day, 18 m / min and inclination of 10 ) for 8 weeks. Then animals from INF EX and INF SED had the left descending coronary artery occluded with a suture thread. The same procedure was performed with SHAM animals, but without artery occlusion. Fifteen days after MI induction myocytes located at the border zone (2mm) of the infarcted area were isolated from some animals of each group and stimulated at 0.5 and 3 Hz at room temperature (~ 25 C) to measure cell contractile function at different extracellular calcium (0.6, 1 e 5 mM). The remaining animals were used to obtain hemodynamic records. After this procedure, the hearts were removed, fixed and stained with picrosirius red and Masson Trichrome for histological analysis. The results show that the exercised animals had a better running capacity than the sedentary ones (P <0.05). Treadmill running reduced the mortality of infarcted animals, but without statistical difference (P <0.05). Body weight, heart weight, relative weight of heart, lung weight, relative lung weight and lung fluid were not affected by the exercise program (P <0.05). However, the infarct size and collagen content in the surviving myocardium were reduced in previously exercised animals, although the capillary density was not changed (P <0.05). The length, width and cell volume were greater in INF EX group (P <0.05), compared to INF-SED. Exercised animals showed higher contraction amplitude and maximal velocity of contraction and relaxation when compared to sedentary control group (P <0.05). Furthermore, treadmill running increased the dP / dt + and reduced the xiii dP/dt- (P <0.05). It was concluded that the program of treadmill running attenuated the deleterious effects caused by MI on the morphology and contractile function of the myocardium. The main adaptations of exercise program were: a) attenuation of the changes in the amplitude of cell contraction and improvement of the contraction- relaxation cycle; b) increases in the length, width and volume of cardiomyocytes, c) reduction of collagen deposition in the surviving myocardium; and e) attenuation of the changes in the hemodynamic parameters.

ASSUNTO(S)

exercício físico infarto do miocárdio cardiomiócitos contratilidade cardíaca biologia geral physical exercise myocardial infarction cardiomyocytes cardiac contractility

ACESSO AO ARTIGO

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