Angiotensin-(1-7) upregulates cardiac nitric oxide synthase in spontaneously hypertensive rats.
It has been shown that angiotensin (ANG)-(1-7) activates nitric oxide synthase (NOS) in isolated ventricular myocytes from normotensive rats. Since many ANG-(1-7) actions are enhanced in situations of increased ANG II activity, as in hypertension, in this study we investigated the in vivo effect of ANG-(1-7) on NOS activity and expression of endothelial (eNOS), neuronal (nNOS), and inducible NOS (iNOS) in ventricles from spontaneously hypertensive rats (SHR). Rats were subjected to a 60-min ANG-(1-7) infusion (0.35 nmol/min); controls received saline. NOS activity was measured using the NADPH diaphorase histochemical method and by the conversion of L-[(14)C]arginine to citrulline, and NOS phosphorylation and expression were determined using Western blotting. In SHR, ANG-(1-7) infusion diminished mean arterial pressure from 180 ± 9 to 146 ± 9 mmHg (P < 0.05), and this effect was prevented by nitro-l-arginine methyl ester (l-NAME), a NOS inhibitor. In addition, NOS activity and eNOS phosphorylation were increased by ANG-(1-7) infusion. Ventricular eNOS and nNOS expression were increased 67.4 ± 6.4 and 51 ± 10%, respectively, by ANG-(1-7), whereas iNOS was not changed. In another set of experiments, we evaluated the mechanism by which ANG-(1-7) modifies NOS activity. Isolated ventricle slices preincubated with ANG-(1-7) showed an increase in NOS activity and eNOS phosphorylation, which was blocked by an AT(2) and a bradykinin B(2) receptor antagonist, but not by the Mas receptor antagonist. Our results show that in rats in a hypertensive state, ANG-(1-7) infusion upregulates cardiac NOS expression and activity through an AT(2)- and bradykinin-dependent mechanism. In this way ANG-(1-7) may elicit its cardioprotective action and contribute to some of the counterregulatory AT(2) receptor effects that oppose the AT(1) receptor-mediated effects.
Costa
María A
MA
Cátedra de Fisiología, Instituto de Química y Metabolismo del Fármaco, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina.
Lopez Verrilli
María A
MA
Gomez
Karina A
KA
Nakagawa
Pablo
P
Peña
Clara
C
Arranz
Cristina
C
Gironacci
Mariela M
MM
D000803:Angiotensin I / Q000494:pharmacology*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001920:Bradykinin / Q000378:metabolism; D004195:Disease Models, Animal; D006352:Heart Ventricles / Q000378:metabolism; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D010766:Phosphorylation; D051381:Rats; D011918:Rats, Inbred SHR; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects*
D000959:Antihypertensive Agents; D010446:Peptide Fragments; D044139:Receptor, Angiotensin, Type 2; D000803:Angiotensin I; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C118790:angiotensin I (1-7); D001920:Bradykinin