NEW INSIGHTS INTO THE GENERATION OF THE ANGIOTENSIN PEPTIDES

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

Different modulatory effects of ammonium ions on angiotensin vascular actions in isolated rat aortic and renal arteries

In the present study, we were interested in the vascular effects of angiotensin II on perfused rings of the rat thoracic aorta and renal artery. Our results demonstrated different modulator alterations of these preparations induced by ammonium ions. Unlike the aortic rings, which exhibited only a reduction of angiotensin-induced contractility by NH4Cl, the renal artery preparations showed both activation of vasoconstriction and inhibition of vasorelaxation in the ring precontracted with phenylephrine or noradrenalin. These results are interpreted as a modulation by the ammonium ions of vascular reactions induced by the stimulation of the vasoconstrictor AT1 receptor on the one side and AT2 vasodilator receptors on the other. The potentiation of renal vasoconstriction accompanied by the reduction of angiotensin vasodilation by NH4Cl suggests the possibility of involvement from the blood flow and renal vascular tonus disturbances induced by ammonium ions during hyperammonemia of various causes