Efeitos da infecção experimental com Trypanosoma cruzi sobre a morfologia do miocárdio, propriedades mecânicas de cardiomiócitos isolados e tolerância ao exercício físico de ratos Wistar

• Autor(a) principal: Novaes, Rômulo Dias
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2325
• topic: Tolerância ao exercício; Trypanosoma cruzi; Doença de Chagas; Morfologia do miocárdio; Contratilidade de cardiomiócitos; Exercise tolerance; Trypanosoma cruzi; Chagas’ disease; Myocardium morphology; Cardiomyocytes contractility; CNPQ::CIENCIAS BIOLOGICAS::BIOLOGIA GERAL

Trypanosoma cruzi (T. cruzi), an intracellular protozoan parasite, is the causative agent of Chagas’ disease. This parasite is able to alter the morphology and hemodynamics of the heart, changes that have been implicated in the reduction of exercise tolerance in individuals with Chagas’ disease. Changes in cardiomyocyte mechanics in this disease have been rarely reported and the role of these changes in exercise tolerance remains unknown. Thus, the present study investigated the effects of experimental Trypanosoma cruzi infection on myocardium morphology, mechanical properties of isolated cardiomyocytes and exercise tolerance in Wistar rats. Twenty-eight male Wistar rats were divided into an uninfected (n=14) and an infected group (n=14). After nine weeks of inoculation with trypomastigote forms of T. cruzi, animals were subjected to an incremental running protocol to evaluate the physical performance. Then, hearts were removed for histopathological and morphometric analysis and cardiomyocytes were isolated by enzymatic dispersion for analysis of mechanical properties. The results showed that T. cruzi infection impaired exercise tolerance resulting in a significant reduction in distance traveled, total time to fatigue and workload. In the heart of infected animls it was observed the presence of inflammatory infiltrate, hypertrophy of the ventricles and the left ventricular cardiomyocytes, increase of collagen and blood vessels amount and impairments in cellular mechanics. Atrial and ventricular myocytes from infected animals showed a significant reduction of contraction amplitude, maximal rate of contraction and relaxation and increase in time to half relaxation. These ventricular myocytes also showed increased time to peak of contraction. According to these results it was possible conclude that the dysfunction of cardiomyocytes contractility induced by T. cruzi infection occurs in an environment morphologically altered and these changes may be associated with reduction of exercise tolerance in infected rats.