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Overview of the Renin-Angiotensin System

Well, turns out our bodies have a pretty great system for making sure that our blood pressure always stays in check as our diets change, we get stressed, or we inevitably forget to drink enough water.

Inside our bodies, our good friends the liver and the kidney are hard at work making angiotensinogen, a peptide and an enzyme called renin. Both are released into the bloodstream where renin cleaves off three amino acid subunits (or residues) from the end of angiotensinogen to make a new peptide called angiotensin. And... this really cool “keep your blood pressure normal system” is really called the renin-angiotensin system (or sometimes the renin-angiotensin-aldosterone system).

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Featured

 Basic Review: The Renin-Angiotensin-Aldosterone Axis

One of the coolest aspects of the renin-angiotensin-aldosterone system (RAAS) is that it involves multiple organ systems: the liver, lung, adrenal gland, kidney, and vasculature are all prominently involved. It never hurts to review basic physiologic principles, right?

 What Does The Renin-Angiotensin-Aldosterone System (RAAS) Have To Do With Long COVID?

Although there are no studies confirming this link, does this lack of vasoconstriction lead to the development of long COVID? What is certain is that the suppression of ACE2 leads to harmful hypertension in these COVID patients. There is also evidence that oestrogen regulates the expression of ACE2 in the body, so potentially patients who have decreased oestrogen, for reasons such as menopause, become exponentially more at risk of long COVID due to the lack of ACE2 (American Physiological Society, 2020). This could explain why middle-aged women are seemingly most likely to be affected by long COVID.

 Why the renin–angiotensin–aldosterone system (RAAS) in critically ill patients can no longer be ignored

There are profound and clinically relevant disturbances of the RAAS in critically ill patients, detected by the presence of hyperreninemia. Depending on the time of renin measurement and the population, this hormone may be associated with the development of AKI or an increased mortality or both. In addition, the vasodilatory biotype of high-renin shock may, in the future, be further defined by the mechanisms responsible for hyperreninemia. Irrespective of the mechanisms, however, personalized treatment of critically ill patients who have high renin-levels with AT-II might improve outcome. The importance and complexity of the RASS in critical illness can no longer be ignored.

Articles of Interest

Association Between Renin-Angiotensin-Aldosterone System Inhibitors and Clinical Outcomes in Patients With COVID-19

In this systematic review and meta-analysis of 52 studies that evaluated clinical outcomes among 101 949 total patients with COVID-19 who did and did not receive ACEIs or ARBs, a significantly lower risk of multivariable-adjusted mortality and severe adverse events was found among patients who received ACEIs or ARBs compared with patients who did not.

Drugs targeting the renin–angiotensin–aldosterone system

Approved drugs that act on the RAAS that are discussed here include ACE inhibitors, AT1-receptor blockers (ARBs) and aldosterone-receptor antagonists (ARAs).

The Renin Angiotensin Aldosterone System (Club RAAS)

Welcome to the renin angiotensin aldosterone system, or Club RAAS, where you’ll get a dose of crucial information about ACE inhibitors and the elements responsible for the system’s regulation.

The Renin-Angiotensin System and Blood Pressure Control

The renin-angiotensin system or RAS regulates blood pressure and fluid balance in the body. When blood volume or sodium levels in the body are low, or blood potassium is high, cells in the kidney release the enzyme, renin.

The Renin-Angiotensin-Aldosterone System in Postmenopausal Women: The Promise of Hormone Therapy

The RAAS is an immunomodulating system that is critical for maintaining homeostasis across multiple organ systems.

The Role of Renin-Angiotensin-Aldosterone System in the Heart and Lung: Focus on COVID-19

The renin-angiotensin-aldosterone system (RAAS) firstly considered as a cardiovascular circulating hormonal system, it is now accepted as a local tissue system that works synergistically or independently with the circulating one.

Your Renin-Angiotensin-Aldosterone System And Why It's Important

Two other crucial (and interrelated) parameters that we regulate through homeostasis are: blood pressure and blood volume. To control these two parameters, we’ve evolved a complex hormonal system involving communication between our brain, lungs, liver and kidneys. This hormonal system is known as the renin-angiotensin-aldosterone system (RAAS).

Resources

Journal of the Renin-Angiotensin-Aldosterone System

Journal of the Renin-Angiotensin-Aldosterone System (JRAAS) is a peer-reviewed open access journal which focusses on the normal and abnormal function of the renin-angiotensin-aldosterone system and its pharmacology and therapeutics, mostly in a cardiovascular context but including research in all areas where this system is present, including the brain, lungs and gastro-intestinal tract.

Medicine Hack

Angiotensinogen, the precursor of all angiotensin peptides, is synthesized by the liver. In the circulation it is cleaved by renin, an acid protease, which is secreted into the lumen of renal afferent arterioles by juxtaglomerular cells. Renin is synthesized as a large preprohormone called as preprorenin. It is then cleaved to prorenin and eventually to renin. Prorenin is also secreted by other organs like ovaries. But, conversion to renin is almost exclusively the job of the kidney.

Cardiovascular Physiology Concepts

The renin-angiotensin-aldosterone pathway is not only regulated by the mechanisms that stimulate renin release, but it is also modulated by natriuretic peptides released by the heart. These natriuretic peptides act as an important counter-regulatory system.

Medical Exam Prep

The first stage of the RAAS is the release of the enzyme renin. It is released from juxtaglomerular cells that are situated in the afferent arterioles of the kidney in response to the following stimuli...

Teach Me Physiology

The system is mainly comprised of the three hormones renin, angiotensin II and aldosterone. Primarily it is regulated by the rate of renal blood flow.