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The angiotensin pathway, also known as the renin angiotensin-aldosterone system (RAAS), refers to the body’s system of blood pressure regulation, which is controlled primarily by the kidneys. Whenever there is a drop in blood pressure within the body, the kidneys produce an enzyme called renin that signals the body to constrict blood vessels, increasing blood flow to the kidneys. A series of other chemical reactions takes place involving blood pressure, water absorption and heart rate. It is thought that by controlling elements along the angiotensin pathway, hypertension may also be regulated.
Calculations determine that every drop of blood in the human body passes through the kidneys around 350 times a day. During this process, the kidneys filter chemicals and reabsorb water to maintain the proper balance in the biological system. The kidneys require a high volume of pressure to maintain blood flow and accomplish this task.
When blood pressure drops, the kidneys release renin, which then reacts with angiotensinogen to form angiotensin I. When it passes through the lungs, angiotensin I encounters an angiotensin-converting enzyme (ACE) that converts it to angiotensin II. Angiotensin II then signals the body to: constrict all blood resistance vessels; release the hormone aldosterone, which causes the kidneys to reabsorb water and sodium; release the antidiuretic hormone (ADH) vasopressin in the pituitary, which signals fluid retention; stimulate thirst; signal norepinephrine, or nor-adrenaline, release; and increase heart rate.
When sodium (Na+) levels increase in the bloodstream, the heart secretes an atrial natriuretic peptide (ANP) that stimulates urination and excretion of sodium. This peptide also inhibits the secretion of aldosterone, renin and vasopressin. This functions as a check against the kidney’s hypertensive activity but also places additional strain on the heart.
Drugs that attempt to control hypertension include ACE inhibitors, angiotensin receptor blockers, renin inhibitors and aldosterone receptor antagonists. Although some success has been achieved in regulating blood pressure with these drugs, much is not understood regarding the body’s complex mechanisms and self regulation. In many cases, an application that produces a desired effect will create a number of reactions that have detrimental effects. Some ACE inhibitors have been implicated in heart damage.
The angiotensin pathway is only one of the body’s many complex chemo-electrical, biological systems. While much has been learned about how the human body functions, more knowledge is needed. In the meantime, the simplest, most efficient method for proper regulation of all of these systems, including the angiotensin pathway, remains a healthy diet and proper exercise.