Other Angiotensins

Besides the major role of angiotensin II (Ang II) in the renin-angiotensin system (RAS), other angiotensin peptides with different lengths were recently discovered to be biologically active and they possess individual receptors and signaling pathways. Ang III stimulates AT1 and AT2 receptors and its signaling pathway is similar to that of Ang II but has a specific role on aldosterone stimulation in adrenal cortex. The Ang(1–7)/Mas receptor axis is known to antagonize the effects of the AT1 axis. These include anti-hypertrophic action, anti-thrombotic and anti-fibrotic effect, and vasodilation via stimulation of NO synthesis in endothelium and potentiation of the bradykinin effect. Ang IV stimulates insulin-regulated aminopeptidase (IRAP) or AT4 receptor and is involved in facilitation of memory such as reversing memory deficits caused by alcohol abuse and ischemia. AT4 antagonist decreases renal blood flow and increases urinary sodium excretion, and these effects are independent of the AT1 pathway.