title: The antithrombotic effect of angiotensin-(1-7) involves mas-mediated NO release from platelets.
abstract: The antithrombotic effect of angiotensin(Ang)-(1-7) has been reported, but the mechanism of this effect is not known. We investigated the participation of platelets and receptor Mas-related mechanisms in this action. We used Western blotting to test for the presence of Mas protein in rat platelets and used fluorescent-labeled FAM-Ang-(1-7) to determine the specific binding for Ang-(1-7) and its displacement by the receptor Mas antagonist A-779 in rat platelets and in Mas(-/ -) and Mas(+/+) mice platelets. To test whether Ang-(1-7) induces NO release from platelets, we used the NO indicator DAF-FM. In addition we examined the role of Mas in the Ang-(1-7) antithrombotic effect on induced thrombi in the vena cava of male Mas(-/ -) and Mas(+/+) mice. The functional relevance of Mas in hemostasis was evaluated by determining bleeding time in Mas(+/+) and Mas(-/ -) mice. We observed the presence of Mas protein in platelets, as indicated by Western Blot, and displacement of the binding of fluorescent Ang-(1-7) to rat platelets by A-779. Furthermore, in Mas(+/+) mouse platelets we found specific binding for Ang-(1-7), which was absent in Mas(-/ -) mouse platelets. Ang-(1-7) released NO from rat and Mas(+/+) mouse platelets, and A-779 blocked this effect. The NO release stimulated by Ang-(1-7) was abolished in Mas(-/ -) mouse platelets. Ang-(1-7) inhibited thrombus formation in Mas(+/+) mice. Strikingly, this effect was abolished in Mas(-) (/) (-)mice. Moreover, Mas deficiency resulted in a significant decrease in bleeding time (8.50 +/- 1.47 vs. 4.28 +/- 0.66 min). This study is the first to show the presence of Mas protein and specific binding for Ang-(1-7) in rat and mouse platelets. Our data also suggest that the Ang-(1-7) antithrombotic effect involves Mas-mediated NO release from platelets. More importantly, we showed that the antithrombotic effect of Ang-(1-7) in vivo is Mas dependent and that Mas is functionally important in hemostasis.
authors.affiliation: Department of Physiology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Rodrigo Araújo
authors.initials: RA
authors.lastname: Fraga-Silva
authors.forename: Sergio Veloso Brant
authors.initials: SV
authors.lastname: Pinheiro
authors.forename: Andrey Christian Costa
authors.initials: AC
authors.lastname: Gonçalves
authors.forename: Nathalia
authors.initials: N
authors.lastname: Alenina
authors.forename: Michael
authors.initials: M
authors.lastname: Bader
authors.forename: Robson Augusto Souza
authors.initials: RA
authors.lastname: Santos
mesh_terms: D000803:Angiotensin I / Q000378:metabolism / Q000494:pharmacology*; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001760:Bleeding Time; D001777:Blood Coagulation / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000172:deficiency / Q000187:drug effects / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000378:metabolism / Q000494:pharmacology*
chemical_list: C092006:7-Ala-angiotensin (1-7); D010446:Peptide Fragments; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000804:Angiotensin II; D009569:Nitric Oxide; D000803:Angiotensin I; C118790:angiotensin I (1-7)