Angiotensin III

Where it comes from

Made in

Made from angiotensin II by aminopeptidase A, in blood, kidney and brain

Sent out by

Follows angiotensin II

Acts on

• Adrenal cortex
• Brain (vasopressin release, thirst)
• Kidney

What it does

• Releases aldosterone as strongly as angiotensin II, so an aldosterone result reflects both ³
• In the brain it, and not angiotensin II, raises blood pressure and releases vasopressin ¹
• Weaker as a direct constrictor and shorter-lived, because the next aminopeptidase is waiting ¹

In medicine

• No medicine and no test of its own. Assays for angiotensin II generally cannot exclude it, since one residue separates them
• It is the reason the brain arm of this system is treated as a separate problem: blocking angiotensin II in the blood does not reach what angiotensin III does inside the brain ¹

Beyond the body’s own use

• Firibastat, a brain aminopeptidase A inhibitor designed to stop its formation, failed to lower blood pressure meaningfully in difficult-to-treat and resistant hypertension in the FRESH trial, and its development stopped ²
• That failure is the honest summary of the field: a convincing animal story about brain angiotensin III did not survive a randomised trial in people ¹²
• Nothing is in trials now and nothing is claimed for the peptide itself