Role of brain Angiontensin‐(1‐7) in the gene expression of angiotensinergic receptors in the heart

Abstract

Hypertensive rats subjected to chronic intracerebroventricular (ICV) infusion of Angiotensin‐(1‐7) presented attenuation of arterial hypertension, improvement the sensitivity of the baroreflex, restoration the cardiac autonomic tone and alteration the expression of cardiac RAS components. In this study we evaluated whether the acute increase in the brain levels of Ang‐(1‐7) modulates the gene expression of angiotensinergic receptors in the left ventricle of normotensive and hypertensive rats. Sprague‐Dawley (SD) and hypertensive rats that overexpress renin (TGR) were used. The animals were divided into four experimental groups: SD, ICV infusion of saline (3 mL/hour), n=5; SD, ICV infusion of Ang‐(1‐7) (2,5 mg/hour), n=5; TGR, ICV infusion of saline (3 mL/hour), n=4 and TGR, ICV infusion of Ang‐(1‐7) (2,5 mg/hour), n=4. Immediately after the ICV infusion, the animals were euthanized by decapitation and the left ventricle was removed and frozen on dry ice. The mRNA expression of AT1, AT2 and Mas receptor were evaluated by semi quantitative real time‐PCR using the delta delta CT method. The acute infusion of saline or Ang‐(1‐7) for 3 hours did not alter the gene expression of AT1 and Mas receptors in the left ventricle of the normotensive or hypertensive rats. In contrast, the acute infusion of Ang‐(1‐7) was capable of increasing the gene expression of AT2 receptors in SD (2.78±0.55 a.u. vs.1.17±0.35 a.u. in ICV saline group) and TGR(mRen2)27 (3.37±0.92 a.u. vs. 1.05±0.15 a.u. in ICV saline group). Short‐term ICV infusion of Ang‐(1‐7) in the brain alters gene expression of the AT2 receptor in the left ventricle of normotensive and hypertensive rats.