Role of the renin-angiotensin system on cardiovascular and metabolic effects induced by chronic stress in rats

Author(s)

Andrea Sanches

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2012-02-23

Examining board members

Tatiana de Sousa da Cunha; Elenice Aparecida de Moraes Ferrari; Danielle Yuri Arita

• Advisor: Fernanda Klein Marcondes; Tatiana de Sousa da Cunha

Abstract

Chronic stress is a risk factor for the development of hypertension, atherosclerosis and diabetes. The protocol of chronic mild and unpredictable stress (CMUS) is an animal model of chronic stress. Previously, it has been shown that CMUS induced insulin resistance, dyslipidemia and endothelial dysfunction in rats. Considering that endothelial dysfunction and insulin resistance have been associated with high activity of renin-angiotensin system (RAS), the aim of this study was to investigate the involvement of RAS components on cardiovascular effects induced by CMUS in rats. Sixty two male Sprague-Dawley rats, (2 months old) were used. The experiment period was 7 weeks. In experiment 1, animals were divided into 2 groups: control and stress. The CMUS was applied on weeks 3, 4 and 5 and animals were euthanized 1 and 15 days after the CMUS. The CMUS increased systemic renin and angiotensin converting enzyme (ACE) activity, ACE activity in the thoracic aorta and plasma angiotensin II and angiotensin (1-7) concentrations. Based on these results, showing increased activity of the RAS induced by ECMI, the second experiment was designed to evaluate the involvement of angiotensin II and its AT1 receptor in the effects triggered by CMUS on glucose uptake and on cardiovascular system. Other animals were divided into 4 experimental groups: control, stress, losartan control (AT1 receptor antagonist, losartan - 50 mg /kg/day, orally) and losartan stress. The CMUS induced an increase in area under the curve in the glucose tolerance test (GTT), decreased the in vitro vasodilator response to acetylcholine in the thoracic aorta and increased blood pressure, compared to control group, without difference among control, losartan control and losartan stress group. These results show that the effects of CMUS led to endothelial dysfunction in rats, which was positively associated with hyperactivity of the RAS and was canceled by the treatment with losartan. Thus, this study explains part of the physiological mechanisms involved in cardiovascular and metabolic changes resulting from chronic stress, demonstrating that these changes are mediated by the AT1 receptor, probably by angiotensin II binding to it (AU)

• FAPESP's process: 09/13144-5 - Role of renin-angiotensin-system on cardiovascular effects induced by chronic stress in rats
• Grantee: Andrea Sanches
• Support Opportunities: Scholarships in Brazil - Master