Medical Definition of angiotensin I
: the physiologically inactive form of angiotensin that is composed of 10 amino acid residues, is derived from angiotensinogen, and is converted by angiotensin converting enzyme to angiotensin II <Angiotensin I is a decapeptide without apparent physiologic effect. In a single passage through the pulmonary circulation, angiotensin I is cleaved by a membrane-bound converting enzyme to produce angiotensin II, a very potent vasoconstrictor.—Scientific American Medicine, September 1982>
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