Schematic representation of the renin-angiotensin system (RAS). ACE: angiotensin-converting enzyme; ACE2: angiotensin-converting enzyme 2; NEP: neprilysin; AT1R: Ang II type 1 receptor. Angiotensinogen is cleaved by renin in the circulation to generate Ang I. Ang I is cleaved to yield Ang II by ACE, Ang-(1-7) by NEP, or Ang (1-9) by ACE2; this reaction is much less favourable than the production of Ang-(1-7) from Ang II. Ang-(1-9) is then cleaved by either NEP or ACE to yield Ang-(1-7) in a minor pathway. Ang II exerts its main actions by binding to the AT1R. Ang II can also be further cleaved by ACE2, into Ang-(1-7), which exerts its effects through its receptor (Mas). The opposing actions of the two receptors are listed above.
