Renin–angiotensin–aldosterone system

The renin–angiotensin–aldosterone system is a hormone cascade that helps regulate blood pressure, sodium balance, and body-fluid volume. It links signals from the kidneys to blood-vessel constriction and changes in kidney reabsorption.

Renin: An enzyme released mainly by kidney cells that initiates angiotensin production from angiotensinogen. Reduced kidney perfusion, sodium delivery, or sympathetic input prompts renin release and starts the cascade.
Juxtaglomerular apparatus: A kidney structure comprising renin-producing cells, the macula densa, and supporting mesangial cells. It integrates pressure, sodium chloride, and neural signals that regulate renin secretion.
ACE inhibitor: A drug that inhibits angiotensin-converting enzyme and reduces angiotensin II formation. This treatment lowers signaling through a major step in the classic cascade.
Hypertension: A chronic condition in which arterial blood pressure is persistently elevated. Excessive or sustained system activity can contribute to elevated vascular resistance and blood volume.
Angiotensin-converting enzyme: An enzyme that converts angiotensin I into angiotensin II, especially on endothelial surfaces. It performs the key conversion that generates the system’s main pressor hormone.
Angiotensinogen: A circulating protein produced mainly by the liver that renin cleaves to form angiotensin I. It is the substrate on which renin acts to initiate the peptide sequence.
Angiotensin II receptor blocker: A drug that blocks angiotensin II type 1 receptors. It limits a principal angiotensin II effect without inhibiting peptide formation.
Edema: An abnormal accumulation of fluid in interstitial tissues or body cavities. Sodium and water retention can expand fluid volume and aggravate tissue swelling.
Angiotensin II: A peptide hormone that constricts blood vessels and promotes aldosterone release, thirst, and sodium retention. This central effector raises vascular resistance and coordinates several downstream responses.
Sympathetic nervous system: The autonomic division that mobilizes bodily responses through neural signals and catecholamines. Sympathetic stimulation of kidney β1 receptors can increase renin release.

Linked from 44 pages