Angiotensin III (Ang III) is a heptapeptide agonist at the angiotensin 1 (AT1) and AT2 receptors, with a 30-fold higher affinity for AT2 compared with AT1 in HEK293 cells. Ang III is the preferred agonist for renal AT2 receptors, which are responsible for sodium excretion into the urine. Ang III induces the same level of aldosterone synthesis as Ang II but has lower vasoconstrictive activity in vivo. In the brain renin-angiotensin system, Ang III increases sympathetic nerve activity and vasopressin release and dampens the baroreflex leading to higher blood pressure.
