Sistema renina-angiotensina em tecidos de camundongos espontaneamente diabéticos

• Autor(a) principal: Colucci, Juliana Almada [UNIFESP]
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: http://repositorio.unifesp.br/handle/11600/10096
• topic: Camundongos; Enzima conversora de angiotensina-I; Diabetes Mellitus; Peptidil Dipeptidase A

The renin angiotensin system (RAS) is a coordinated cascade of proteins and peptide hormones that play a role in regulating blood pressure and fluid balance and electrolytes in mammals. In the classical pathway of RAS, renin, which is secreted by the juxtaglomerular apparatus of the kidney, in response to a wide variety of stimuli, acts on the precursor angiotensinogen (AGT) to generate the decapeptide angiotensin-I (AI). AI has little, if any, action on blood pressure, but is rapidly converted to angiotensin-II (AII) by angiotensinconverting enzyme I (ECA). AII has multiple direct renal actions, including arterial vasoconstriction, stimulation of sodium reabsorption and inhibition of pressure natriuresis via AT1 receptor. The close relationship between RAS and the endocrine system is increasingly enhanced by the prominent role of AII in diabetes. Diabetes mellitus (DM) is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, in its action, or both. In our study, we associate diabetes to RAS using different tissues of non-obese diabetic mouse, a spontaneous model of type 1 diabetes, thus verifying the behavior of such a system in non-induced diabetes. In general, renal morphological changes were not identified in our model by histology, although it was possible to identify mild urinary albumin excretion. The hemodynamic parameters of the groups and NOD H and NODN revealed significant decreases in blood pressure and heart rate of diabetic animals. However, by immunohistochemistry we observed strong tubular expression of ACE. Furthermore, we found that the RAS is activated in the diabetic group, mainly in the kidney, a major target of our study. The measurement of ACE activity proved to be increased in the diabetic kidney tissue, lung and adrenal, reduced in pancreatic tissue and was not significantly altered in heart or liver. Despite significant changes in renal ACE activity, levels of AII, AI and Ang1-7 and had not changed, while the quantification of BK showed significant increase of this peptide in diabetic animals. Finally, we decided to perform primary cell cultures and ss in the kidney homogenate, cell lysates of the NOD H group showed an increase in ACE activity and, moreover, the same material exhibited reduced activity of NEP. By analyzing the hydrolysis of AII into Ang1-7 from the culture medium, we concluded that it was decreased in the diabetic group, indicating a possible decrease on ACE2 activity. Therefore, in general, the results found on this study support the hypothesis that the RAS is activated in diabetes and reveal a new field of application for the NOD model.