Val(5)- Angiotensin II:The active form of angiotensin. An octapeptide found in blood, it is synthesized from ANGIOTENSIN I and quickly destroyed. Angiotensin II causes profound vasoconstriction with a resulting increase in blood pressure. It differs among species by the amino acid in position 5. The human form has ISOLEUCINE in this position. The clinically and experimentally used bovine form has VALINE in position 5.