Many studies have shown that risk factors that are independent of blood pressure (BP) can contribute to the development of cardiac hypertrophy (CH). Among these factors, high-salt (HS) intake was prominent. Although some studies have attempted to elucidate the role of salt in the development of this disease, the mechanisms by which salt acts are not yet fully understood. Thus, the aim of this study was to better understand the mechanisms of CH and interstitial fibrosis (IF) caused by HS intake. Male Wistar rats were divided into 5 groups according to diet [normal salt (NS; 1.27% NaCl) or HS (8% NaCl)] and treatment [losartan (LOS) (HS+LOS group), hydralazine (HZ) (HS+HZ group), or N-acetylcysteine (NAC) (HS+NAC group)], which was given in the drinking water. Tail-cuff BP, transverse diameter of the cardiomyocyte, IF, angiotensin II type 1 receptor (AT1) gene and protein expression, serum aldosterone, cardiac angiotensin II, cardiac thiobarbituric acid-reactive substances, and binding of conformation-specific anti-AT1 and anti-angiotensin II type 2 receptor (AT2) antibodies in the 2 ventricles were measured. Based on the left ventricle transverse diameter data, the primary finding was the occurrence of significant BP-independent CH in the HS+HZ group (96% of the HS group) and a partial or total prevention of such hypertrophy via treatment with NAC or LOS (81% and 67% of the HS group, respectively). The significant total or partial prevention of IF using all 3 treatments (HS+HZ, 27%; HS+LOS, 27%; and HS+NAC, 58% of the HS group, respectively), and an increase in the AT1 gene and protein expression and activity in groups that developed CH, confirmed that CH occurred via the AT1 in this experimental model. Thus, this study unveiled some relevant previously unknown mechanisms of CH induced by chronic HS intake in Wistar rats. The link of oxidative stress with CH in our experimental model is very interesting and stimulates further evaluation for its full comprehension.
Objective To evaluate the early and late effects of N-acetyl-l-cysteine (NAC) treatment on renal ischemia and reperfusion (I/R) insult in adult Wistar rats influenced by chronic high sodium (HS) intake. Methods Adult male Wistar rats (8 weeks of age) received an HS (8.0% NaCl) or normal sodium (NS; 1.3% NaCl) diet and NAC (600 mg/L) in drinking water or normal water. At 11 weeks of age, the rats underwent a renal I/R procedure. They followed for 10 weeks after I/R, at the 1st, 2nd, 4th, and 10th weeks, in which tail blood pressure (tBP) and renal function were evaluated. And renal renin gene expression was evaluated in the 10th week after I/R. Results During the study, it was observed that the tBP remained consistently higher in the HS-I/R+water group compared to the NS-I/R+water group. However, in the early weeks following I/R (1st, 2nd, and 4th weeks), the tBP was lower in the HS-I/R+NAC group than in the HS-I/R+water group. In the 10th week after I/R, the serum creatinine levels were higher in both the HS-I/R+NAC and NS-I/R+NAC groups compared to the HS-I/R+water and NS-I/R+water groups. Conversely, the creatinine clearance was higher in the HS-I/R+NAC group than in the HS-I/R+ group in the 2nd week following I/R. Additionally, the urinary protein levels were higher in the HS-I/R+NAC group than in the NS-I/R+NAC group in the 10th week after I/R. It was also observed that NAC treatment resulted in increased renal renin gene expression in the 10th week following I/R. Conclusions After renal I/R in animals given HS, NAC treatment was initially effective in lowering blood pressure or increasing creatinine clearance. However, these positive effects did not persist over the long term, resulting in decreased kidney function and increased blood pressure. Furthermore, the renin-angiotensin-aldosterone system was increased by HS intake, and the benefits of the NS diet were less effective than those of the HS diet. Thus, NAC provides temporary protection only in the early stages following an insult.
Á minha família, por todo amor, zelo, esforços e sacrifícios feitos por mim! Obrigado por tudo! AGRADECIMENTOS Dra. Luzia Naoko Shinohara Furukawa pela orientação, pela paciência e por tentar nos ajudar sempre! Obrigado por me aceitar como aluno, a levarei sempre com carinho. À Carolina M. Romão, por dividir comigo durante esses quatro anos todas as tristezas, mágoas, dificuldades, assim como as alegrias, as satisfações e as gratificações deste projeto. Levarei para sempre sua amizade com carinho! A Ivone Braga de Oliveira pelas brincadeiras, amizade e apoio! Muito obrigado! À Drª Maria Heloísa Shimizu pelas dosagens de TBARS e pelas dúvidas sanadas durante o percurso! À Drª Isis Akemi Katayama Rangel, a quem me aceitou como aluno de iniciação científica. Agradeço pelos conselhos, amizade e pela oportunidade de entrar no mundo da pesquisa. Ao Guilherme Marchesi, pela amizade que levo com carinho e pelo suporte técnico no projeto. Muito obrigado! Ao Prof. Dr. Joel C. Heimann, obrigado pela oportunidade, pela confiança e por todos estes anos de aprendizado.
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