The Renin-Angiotensin-Aldosterone System

The renin—angiotensin—aldosterone system (RAAS) is one of the oldest hormonal systems—regardless of whether ‘old’ is defined as phylogenetically old, or in the sense of being discovered a long time ago. Originally, the RAAS has been described as a circulating endocrine system, with angiotensinogen being released by the liver, and renin secreted from the juxtaglomerular apparatus of the kidney, both ‘joining’ in the circulation for processing of angiotensin I. For some forms of secondary hypertension, the activation of the RAAS is an obvious and well-examined pathophysiological mechanism. In 2007, aliskiren was approved as first-in-class direct renin inhibitor, thus introducing a new method of pharmacological interference with the RAAS into the clinics. The gene encoding the renin precursor preprorenin is localized on chromosome Iq32. Renin is primarily released by the juxtaglomerular apparatus of the kidney. Renin secretion is under tight control of several parameters, such as blood pressure and blood volume, plasma sodium content, and sympathetic activation.