Medical Monday: Renin Angiotensin Aldosterone System (RAAS)

keyanazahiri
2 days ago
2 min read

Good morning everyone! Welcome back to another segment of Medical Monday. This month we have been diving into all things blood pressure related. Today, we will be briefly discussing the Renin Angiotensin Aldosterone System (RAAS), one of the most important systems in our body that controls blood pressure, electrolytes, and fluid balances. RAAS is a complex cascade that consists of several stages that are all key targets for several common cardiac medications. It consists of several enzymes and hormones. Enzymes are proteins that facilitate chemical reactions in your body, and hormones are chemicals that facilitate different body functions by acting as messengers throughout your blood, tissues, organs, and more.

There are several different organs and tissues that play a role in the RAAS such as your blood vessels, kidneys, lungs, liver, adrenal glands, and more. Three main body states activate the RAAS system to stabilize the blood pressure in our body: a drop in blood pressure or blood volume, low salt levels in our body, or an increase in sympathetic tone, which is closely related to our body’s “fight or flight” systems. Detection of any of these three states will trigger the kidneys to release an enzyme called renin, that then functions to convert the protein angiotensinogen from the liver into a hormone called angiotensin I. After this, the lungs release an enzyme called ACE (Angiotensin Converting Enzyme), that serves to turn angiotensin I into angiotensin II. Finally, angiotensin II triggers the release of aldosterone from the adrenal glands that sit on top of the kidneys.

All of these enzymes, hormones, and proteins are critical in supporting the RAAS cascade in maintaining our blood pressure at a normal level. Angiotensin II in specific directly acts to increase our fluid volumes and subsequently raise our blood pressure by constricting our blood vessels and triggering release of ADH (Antidiuretic Hormone), which along with aldosterone works to make your kidneys hold onto sodium and water, increasing your blood volume and blood pressure.

This system is critical in long term regulation of blood pressure, and failure of RAAS is an important component of many heart diseases. Many medications have been developed to support and manipulate different components of this cascade to improve cardiac health for patients, such as ACE inhibitors (ex. Lisinopril, Captopril, Lotensin, etc.), Angiotensin receptor blockers (ex. Losartan, Valsartan, Telmisartan, etc.), and mineralocorticoid receptor blockers (ex. Spironolactone, Eplerenone, Finerenone, etc.).

That wraps up our discussion of RAAS! This is a rather complex system, so feel free to reread this article, refer back to our previous blog posts, or reach out for additional resources or clarifications to help with gaining a broad understanding of this system.