GIRONACCI Mariela Mercedes
Angiotensin-(1-7) inhibits the angiotensin II-enhanced norepinephrine release in coarcted hypertensive rats
13. MM GIRONACCI, I YUJNOVSKY, S GORZALCZANY, C TAIRA, C PEÑA
Año: 2004 vol. 118 p. 45 - 49
Since it has been suggested that angiotensin (Ang) (1?7) functions as an antihypertensive peptide, we studied its effect on the Ang IIenhanced norepinephrine (NE) release evoked by K+ in hypothalami isolated from aortic coarcted hypertensive (CH) rats. The endogenous NE stores were labeled by incubation of the tissues with 3H-NE during 30 min, and after 90 min of washing, they were incubated in Krebs solution containing 25 mM KCl in the absence or presence of the peptides. Ang-(1?7) not only diminished the K+-evoked NE release fromhypothalami of CH rats, but also blocked the Ang II-enhanced NE release induced by K+. Ang-(1?7) blocking action on the Ang II response was prevented by [D-Ala7]Ang-(1?7), an Ang-(1?7) specific antagonist, by PD 123319, an AT2-receptor antagonist, and by Hoe 140, a B2 receptor antagonist. Ang-(1?7) inhibitory effect on the Ang II facilitatory effect on K+-stimulated NE release disappeared in the presence of NN-nitro-L-arginine methylester and was restored by L-arginine. Our present results suggest that Ang-(1?7) may contribute to blood pressure regulation by blocking Ang II actions on NE release at the central level. This inhibitory effect is a nitric oxide-mediated mechanism involving AT2 receptors and/or Ang-(1?7) specific receptors and local bradykinin generation.