Angiotensin II (AngII) is a hormone that is part of the renin-angiotensin system, which helps regulate blood pressure and fluid balance in the body. AngII is produced from angiotensin I through the action of the enzyme angiotensin-converting enzyme (ACE). It acts on blood vessels to constrict them, leading to an increase in blood pressure, and also stimulates the release of aldosterone, a hormone that increases sodium reabsorption in the kidneys, further affecting blood volume and pressure.