reniininangiotensiinijärjestelmä

The renin-angiotensin system, often abbreviated as RAS, is a complex hormonal system that plays a crucial role in regulating blood pressure and fluid balance in the body. It is primarily controlled by the kidneys and involves a cascade of enzymatic reactions and hormone releases.

The system is initiated when the kidneys detect a drop in blood pressure or reduced blood flow. In response, they release an enzyme called renin. Renin then acts on a protein produced by the liver, angiotensinogen, converting it into a peptide called angiotensin I.

Angiotensin I is further processed by an enzyme found mainly in the lungs, angiotensin-converting enzyme (ACE), transforming it into angiotensin II. Angiotensin II is a potent vasoconstrictor, meaning it narrows blood vessels, which directly increases blood pressure.

Beyond its vasoconstrictive effects, angiotensin II also stimulates the adrenal glands to release aldosterone. Aldosterone is a hormone that promotes sodium and water reabsorption in the kidneys, further contributing to increased blood volume and, consequently, higher blood pressure. The RAS also influences thirst, encouraging fluid intake, and can affect heart and blood vessel structure over time. Dysregulation of the renin-angiotensin system is implicated in various cardiovascular diseases, including hypertension, heart failure, and kidney disease.