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(Hypertension. 2005;46:937.)
© 2005 American Heart Association, Inc.

Part 2 Original Articles

Evidence for a Functional Interaction of the Angiotensin-(1–7) Receptor Mas With AT₁ and AT₂ Receptors in the Mouse Heart

Carlos Henrique de Castro; Robson Augusto Souza dos Santos; Anderson José Ferreira; Michael Bader; Natalia Alenina; Alvair Pinto de Almeida

From the Departments of Physiology and Biophysics (C.H.C., R.A.S.d.S., A.P.d.A.) and Morphology (A.J.F.), Federal University of Minas Gerais, Belo Horizonte, Brazil, and the Max Delbrück Center for Molecular Medicine (M.B., N.A.), Berlin-Buch, Germany.

Correspondence to Alvair Pinto de Almeida, PhD, Departamento de Fisiologia e Biofísica, Av Antônio Carlos 6627, IC-UFMG 31 270-901, Belo Horizonte, MG, Brazil. E-mail apa{at}icb.ufmg.br

The aim of this study was to evaluate the angiotensin (Ang)-(1–7) effects in isolated mouse hearts. The hearts of male C57BL/6J and knockout mice for the Ang-(1–7) receptor Mas were perfused by the Langendorff method. After a basal period, the hearts were perfused for 20 minutes with Krebs-Ringer solution (KRS) alone (control) or KRS containing Ang-(1–7) (0.22 pmol/L), the Mas antagonist A-779 (115 nmol/L), the angiotensin type 1 receptor antagonist losartan (2.2 µmol/L), or the angiotensin type 2 receptor antagonist PD123319 (130 nmol/L). To evaluate the involvement of Ang receptors, prostaglandins, and nitric oxide in the Ang-(1–7) effects, the hearts were perfused for 20 to 30 minutes with KRS containing either A-779, losartan, PD123319, indomethacin, or N^G-nitro-L-arginine methyl ester (L-NAME) alone or in association with subsequent Ang-(1–7) perfusion. In addition, hearts from Mas-knockout mice were perfused for 20 minutes with KRS containing Ang-(1–7) (0.22 pmol/L) and losartan. Ang-(1–7) alone did not change the perfusion pressure. Strikingly, in the presence of losartan, 0.22 pmol/L Ang-(1–7) induced a significant decrease in perfusion pressure, which was blocked by A-779, indomethacin, and L-NAME. Furthermore, this effect was not observed in Mas-knockout mice. In contrast, in the presence of PD123319, Ang-(1–7) produced a significant increase in perfusion pressure. This change was not modified by the addition of A-779. Losartan reduced but did not abolish this effect. Our results suggest that Ang-(1–7) produces complex vascular effects in isolated, perfused mouse hearts involving interaction of its receptor with angiotensin type 1- and type 2-related mechanisms, leading to the release of prostaglandins and nitric oxide.

Key Words: receptors, angiotensin • cardiac function • heart • angiotensin antagonist • prostaglandins