Endocrinology. A peptide hormone that is important in the regulation of blood pressure by vasoconstriction. The relatively inactive decapeptide angiotensin I is formed by the action of renin on angiotensinogen. The octapeptide angiotensin II is produced from angiotensin I after the removal of two amino acids by angiotensin-converting enzyme (ACE). It is hydrolyzed to form the heptapeptide angiotensin III in various tissues.
Angiotensin II acts as an vasopressor and raises blood pressure and diminishes fluid loss in the kidney by restricting blood flow. It stimulates the aldosterone secretion by the adrenal cortex and epinephrine and norepinephrine secretion by the adrenal medulla.