The classical concept of Ang II as main pressor angiotensin peptide has undergone experienced
substantial changes in the past few years. Many experimental research have revealed novel aspects of the circulating and
tissue RAS. After a brief introduction concerning the two distinct forms of the angiotensin converting enzyme and
proangiotensin – 12 as a new potential precursor for the formation of bioactive angiotensin peptides, the generation and
actions of the main bioactive fragments of Ang II are also presented. Among them are mentioned the pathways of
formation and biological effects of Ang (1-7), Ang III, Ang IV and Ang V involved in the modulation of the Ang II, the
most active multifunctional hormone of RAS. The inhibitory properties of the ACE2–Ang (1-7)–Mas axis are interpreted
as a counterbalancing mechanism against the eventual deleterious actions of Ang II. As described here, these counter-
regulatory properties provide the self-regulation of RAS, as a unitary and integrated hormone system