Abstract 484: The Vasorelaxing / No Release Effect Of Angiotensin-(1-9) Is Independent Of At2, Mas Or Mrgd Receptors
Angiotensin-(1-9) is a nonapeptide formed by the hydrolysis of angiotensin I by ACE2 that seems to counter-regulate the classical RAS axis. Recent studies suggest that Ang-(1-9) acts via AT2 receptors (AT2R), however the pharmacological tool used to asses this ang-(1-9) /AT2R mediated interaction, is the AT2R antagonist, PD123319, that appears to have a great deal of inespecificity . Two other candidates for the ligation of Ang-(1-9), that have protective effects similar to the AT2R, are the MAS and the recently described MrgD receptor. Thus, in this study we addressed if Ang-(1-9) could be a ligand for AT2, MAS or MrgD receptors using aortic rings taken from AT2 and Mas knockout mice and AT2R or MrgD-transfected CHO cells.
Materials and methods: The endothelium-dependent vasodilatory response to Ang-(1-9) was tested in aortic rings taken from Wild-Type, AT2KO and MASKO mice and Sprague-Dawley rats, pre-contracted with phenylephrine (0.1 umoles/L). NO release from AT2R or MrgD stable transfected CHO cells was evaluated using the NO indicator 4-amino-5 methylamino-2, 7 difluorofluorescein diacetate (DAF-FM) after Ang-(1-9) stimulation.
Results: In aortic rings from SD rats Ang-(1-9) produced a dose-related relaxation (Emax= 15 ± 2.6) which was not modified by A-779 (Emax=12.9 ± 1.9) , the Mas/MrgD antagonist D-Pro7-Ang-(1-7) (Emax= 15.6 ± 1.7); or by PD123319 (Emax= 22.7 ± 5.4) . In aortic rings taken from MasKO there was a minor attenuation of the Ang-(1-9) vasorelaxant effect when compared to the WT, but the response was not abolished. No difference between AT2KO and WT mice was observed regarding the vasorelaxation produced by Ang-(1-9) (Emax= 20.7±2.4 and 20.9 ± 1.3 respectively). Moreover, the vasorelaxing effect of Ang-(1-9) was not affected by the association of PD123319 and D-Pro7-Ang-(1-7).
In addition, the nonapeptide did not stimulate NO production in AT2R-stably transfected CHO cells or MrgD stably transfected cells.
Taken together these results suggest that the vasorelaxation produced by Ang-(1-9) in rodent aortic rings is independent of Mas , AT2R or MrgD receptors.
Author Disclosures: G.S.S. Resende: None. N. Silva: None. D.C. Villela: None. R.A.S. Santos: None.
- © 2014 by American Heart Association, Inc.