Renin-Angiotensin System

The Renin-Angiotensin System (RAS) is a hormone system that regulates blood pressure and fluid balance in the body. It plays a crucial role in maintaining cardiovascular and renal function. Here's how it works:

Key Components:

  1. Renin: This enzyme is produced by the kidneys in response to low blood pressure, low sodium levels, or sympathetic nervous system activation. It converts angiotensinogen (a protein produced by the liver) into angiotensin I.

  2. Angiotensin I: A relatively inactive molecule that is converted into angiotensin II by the Angiotensin-Converting Enzyme (ACE), primarily in the lungs.

  3. Angiotensin II: This is the most active form and has multiple effects:

    • Vasoconstriction: It causes blood vessels to narrow, increasing blood pressure.
    • Aldosterone Secretion: It stimulates the adrenal glands to release aldosterone, which promotes sodium and water retention by the kidneys, further increasing blood volume and pressure.
    • ADH Release: It can stimulate the release of Antidiuretic Hormone (ADH), which also helps retain water in the kidneys.

  4. Aldosterone: A hormone that increases the reabsorption of sodium and water from the kidney tubules, increasing blood volume and pressure.

Role in Hypertension and Disease:

  • Hypertension: Overactivity of the RAS can lead to high blood pressure, contributing to conditions like heart failure, kidney disease, and stroke.
  • Medications: Drugs like ACE inhibitors, angiotensin receptor blockers (ARBs), and renin inhibitors are used to block different parts of the system, lowering blood pressure.

This system is essential for controlling both acute and long-term blood pressure and electrolyte balance.


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