Angiotensin IV

Where it comes from

Made in

Made from angiotensin III by aminopeptidase N, in brain, kidney and vessels

Sent out by

Follows the shorter angiotensins

Acts on

• Hippocampus
• Kidney vessels
• Endothelium

What it does

• Improves learning and memory when given into the brain of a rat ²
• Raised kidney cortical blood flow in rats, though later work reports the opposite
• Raises PAI-1 in endothelium, which is the one effect with a plausible route to thrombosis

In medicine

• No medicine and no test. Its binding site turned out to be an enzyme rather than a classical receptor, which changed how the whole AT4 literature is read ¹
• Because IRAP sits inside the cell and trims other peptides too, what an angiotensin IV analogue actually does is harder to state than for a receptor drug ¹
• It is not measured in practice: these fragments are too short-lived and too close in mass for a routine assay

Beyond the body’s own use

• Given into the brain of a rat it improves spatial learning, and the effect has held up across laboratories. That is the whole basis of the memory claim ²
• IRAP inhibitors and angiotensin IV analogues are studied for memory loss in animals. None has reached a human trial, and no medicine has come of it ¹
• The reported effect on kidney blood flow has gone both ways in different rat studies, which is a fair warning about how firm any of this is