(Science: hormone) a family of oligopeptides ranging in size from angiotensin precursors with 14 amino acids to the active vasoconstrictor angiotensin ii with 8 amino acids, or their analogs or derivatives.
Angiotensinogen (renin substrate) is a 60 kd polypeptide released from the liver and cleaved in the circulation by renin to form the biologically inactive decapeptide angiotensin i. This is in turn cleaved to form active angiotensin ii by angiotensin-converting enzyme (ACE). Angiotensin ii causes contraction of vascular smooth muscle and thus raises blood pressure and stimulates aldosterone release from the adrenal glands. Angiotensin is finally broken down by angiotensinases.