The Cardiovascular System: Angiotensin

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Angiotensin II is an octapeptide which is associated with the cardiovascular system. It maintains blood pressure by vasoconstriction and stimulation of aldosterone secretion. Angiotensin II is synthesized through the renin-angiotensin system (RAS) which is known to be involved in systemic blood pressure control, including the regulation of cerebral blood flow (Mogi, Iwanami, & Horiuchi, 2012). Renin, a product of the juxtaglomerular cells of the kidney, is released into the circulation where it cleaves the angiotensinogen to form angiotensin I. Angiotensin I is cleaved by angiotensin-converting enzyme (ACE) to form the angiotensin II. Apart from the production of angiotensin II in plasma and peripheral organs such as kidney, adrenal gland,…show more content…
Both receptors are differentiated by their selective affinity for different non-peptide ligand although they have the similar binding for angiotensin II (De Gasparo, Catt, Inagami, Wright, & Unger, 2000). Both receptors belong to the seven-transmembrane domain, G-protein coupled receptor family (Saavedra, 2005). However, AT2 receptor shares only 32-34% amino acid identity with the AT1 receptor. AT1 receptor was found in the areas related to neuroendocrine control and autonomic regulation of cardiovascular function and the limbic system (Tsutsumi & Saavedra, 1991). The physiological actions of angiotensin II in the brain, such as regulation of blood pressure, fluid balance, and hormone secretion, are mediated by the AT1 receptor. Additionally, systemic angiotensin II affects the brain functions through AT1 receptors located in the circumventricular organs which are devoid of BBB and derived angiotensin II may act at many sites in the central nervous system located behind the BBB (Unger & Scholkens, 2004). On the other hand, AT2 receptor acts a role in brain organogenesis and in the function of sensory and motor systems (Tsutsumi & Saavedra, 1991). However, the physiological functions of the AT2 receptor are still uncertain (De Gasparo & Siragy, 1999; Saavedra, 2005). Thus, the role of brain angiotensin II appears to be multiple and complex
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