Definition
Angiotensin I is a precursor to angiotensin II, a powerful hormone that raises blood pressure. Think of it as the inactive form of a key blood pressure regulator. It's converted into the active form by an enzyme called ACE (angiotensin-converting enzyme). Angiotensin I has limited direct effect on blood pressure. It's like a before-and-after transformation in the body. It needs ACE to reach its full potential.