Angiotensin II is an essential component of the renin-angiotensin system (RAS), a potent regulator of blood pressure, body fluid and electrolyte homeostasis. In response to lowered blood pressure, the enzyme renin cleaves angiotensinogen to produce angiotensin I (angiotensin 1-10). Angiotensin I is a substrate of ACE (angiotensin converting enzyme) that removes a dipeptide to yield the physiologically active peptide angiotensin II (angiotensin 1-8). Angiotensin II acts directly on vascular smooth muscle as a potent vasoconstrictor, affects cardiac contractility and heart rate through its action on the sympathetic nervous system, and alters renal sodium and water absorption through its ability to stimulate the zona glomerulosa cells of the adrenal corte, Xenopus/Amphibian, to synthesize and secrete aldosterone. Genetic variations in angiotensin II are a cause of susceptibility to essential hypertension (EHT). Essential hypertension is a condition in which blood pressure is consistently higher than normal with no identifiable cause.