Estudo dos efeitos da hipertensão arterial nas alterações morfológicas da valva atrioventricular esquerda (mitral) de ratos hipertensos induzidas por L-NAME

• Autor(a) principal: Rocha, Vinícius Novaes
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/7809
• topic: Mitral valve; Elastic fibers; Collagen fibers; Hypertension, L-NAME; Valva mitral; Fibras elásticas; Fibras colágenas; Hipertensão; L-NAME.; Válvula mitral; Tecido elástico; Colágeno; NG-Nitroarginina Metil Éster; CNPQ::CIENCIAS BIOLOGICAS::MORFOLOGIA::HISTOLOGIA

The heart valves are designed to maintain the unidirectional blood flow and for this reason they have an anisotropic architecture of the extracellular matrix that ensures and maintains proper function under conditions of high and low pressure. The valve disease is a disorder that can affect any of the heart valves, marked by any change in its structure that prevents its proper operation. Studies show that the mechanical stress caused by blood flow may interfere with the organizational structure of cells and extracellular matrix of the valve. This study aimed to investigate the possible structural and ultrastructural changes that hypertension, induced by L-NAME, can cause to the left atrioventricular valve (mitral) from hearts of rats. The animals received L-NAME (40mg/kg/dia), previously diluted in water, for five weeks. At the end of the fifth week euthanasia of animals was performed and the valve parietal fragments were collected and processed for light microscopy (histochemistry) and electron microscopy (ultrastructural histochemistry and ultrastructural immunohistochemistry). It was analyzed the morphological structure of the valves at both structural (light microscopy) and ultrastructural (electron microscopy), as well as the thickness of the valve and quantification (% / area) of the elastic and collagen fibers through the ImagePro-Plus 4.5. The animals treated with L-NAME developed hypertension from the second week of administration of the drug. Structurally, it was possible to identify a disorganization of the elastic and collagen fibers with regions of fragmentation. The hypertension animals showed thicker valve regions than control, plus a smaller amount of collagen fibers. Ultrastructurally, it was identified changes of the endothelium in animals treated with L-NAME, where it presented irregular contours and accumulations of vesicles inside. Furthermore, it was also observed fragmentation of basal lamina, disorientation of collagen fibers, fiber oxytalan accumulation near the endothelium and fragmentation of elastic fibers of the atrial layer. This study concluded that increased blood pressure, characterized by hypertension, causes changes in the morphological structure of the valve, which may be linked in with the synergistic inhibition of nitric oxide synthesis, and may thus undermine its perfect operation.