29 Jul
2011

One of the most important determinants of blood pressure is the renin-angiotensin-aldosterone system (RAAS), which is named for three of the compounds involved in this complex series of biochemical reactions. Although the RAAS plays a role in daily fluctuations in blood pressure, it is also a key player in longer-term regulation, and in hypertension.Here’s how the RAAS system works. Angiotensinogen is a protein produced in the liver on a continuous basis. Renin is an enzyme that is released by the kidneys under conditions of stress, exercise, or certain changes in diet. When angiotensinogen and renin join in the bloodstream, they form angiotensin I. As the blood carrying angiotensin I travels through the lungs, it reacts with angiotensin-converting enzyme (ACE) to form angiotensin II. Angiotensin II has two actions. First, it causes the muscular walls of the arteries, and particularly the arterioles, to contract. This decreases their diameter and drives up blood pressure. Second, angiotensin II prompts the adrenal glands (located on top of the kidneys) to release aldosterone. Aldosterone is a hormone that signals the kidneys to keep more sodium and water in the bloodstream and stop excreting them through the urine. This results in increased blood volume and higher blood pressure. The RAAS is crucial for your health and well-being. Remember, the diameter of your blood vessels and your blood pressure are in constant flux as the needs of your body change from moment to moment, and this is one of the mechanisms that oversees these normal variations. However, when the RAAS pathway becomes overactive, blood pressure is consistently elevated. This is estimated to be the primary cause of high blood pressure in about a third of all people with hypertension.*16/313/5*

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