Renin

Definition

Renin is an enzyme secreted by the kidneys that plays a critical role in the regulation of blood pressure and fluid balance. It initiates the renin-angiotensin-aldosterone system (RAAS) cascade by converting angiotensinogen into angiotensin I.

5 Must Know Facts For Your Next Test

1. Renin release is stimulated by low blood pressure, low sodium content in the kidney filtrate, or sympathetic nervous system activation.
2. Renin converts angiotensinogen, a protein produced by the liver, into angiotensin I.
3. Angiotensin I is further converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE), primarily in the lungs.
4. Angiotensin II causes vasoconstriction and stimulates aldosterone release from the adrenal glands, both of which increase blood pressure.
5. Renin secretion is regulated through a feedback mechanism involving blood pressure, blood volume, and sodium concentration.

Review Questions

• What triggers the release of renin from the kidneys?
• Describe the role of renin in the renin-angiotensin-aldosterone system (RAAS).
• How does angiotensin II affect blood pressure?

Related terms

Aldosterone:

A hormone produced by the adrenal glands that increases sodium reabsorption and potassium excretion in the kidneys.

Angiotensin II: A potent vasoconstrictor formed from angiotensin I that raises blood pressure and stimulates aldosterone release.

ACE (Angiotensin-Converting Enzyme): An enzyme that converts angiotensin I to angiotensin II, playing a crucial role in blood pressure regulation.