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Braz. j. med. biol. res ; 47(9): 789-798, 09/2014. graf
Article Dans Anglais | LILACS | ID: lil-719317

Résumé

We examined the contractile responsiveness of rat thoracic aortas under pressure overload after long-term suprarenal abdominal aortic coarctation (lt-Srac). Endothelium-dependent angiotensin II (ANG II) type 2 receptor (AT2R)-mediated depression of contractions to ANG II has been reported in short-term (1 week) pressure-overloaded rat aortas. Contractility was evaluated in the aortic rings of rats subjected to lt-Srac or sham surgery (Sham) for 8 weeks. ANG I and II levels and AT2R protein expression in the aortas of lt-Srac and Sham rats were also evaluated. lt-Srac attenuated the contractions of ANG II and phenylephrine in the aortas in an endothelium-independent manner. However, lt-Srac did not influence the transient contractions induced in endothelium-denuded aortic rings by ANG II, phenylephrine, or caffeine in Ca2+-free medium or the subsequent tonic constrictions induced by the addition of Ca2+ in the absence of agonists. Thus, the contractions induced by Ca2+ release from intracellular stores and Ca2+ influx through stored-operated channels were not inhibited in the aortas of lt-Srac rats. Potassium-elicited contractions in endothelium-denuded aortic rings of lt-Srac rats remained unaltered compared with control tissues. Consequently, the contractile depression observed in aortic tissues of lt-Srac rats cannot be explained by direct inhibition of voltage-operated Ca2+ channels. Interestingly, 12-O-tetradecanoylphorbol-13-acetate-induced contractions in endothelium-denuded aortic rings of lt-Srac rats were depressed in the presence but not in the absence of extracellular Ca2+. Neither levels of angiotensins nor of AT2R were modified in the aortas after lt-Srac. The results suggest that, in rat thoracic aortas, lt-Srac selectively inhibited protein kinase C-mediated activation of contraction that is dependent on extracellular Ca2+ entry.


Sujets)
Animaux , Mâle , Aorte thoracique/physiopathologie , Coarctation aortique/physiopathologie , Calcium/métabolisme , Endothélium vasculaire/physiologie , Muscles lisses vasculaires/physiopathologie , Protéine kinase C/antagonistes et inhibiteurs , Vasoconstriction/physiologie , Angiotensine-I/analyse , Angiotensine-II/analyse , Aorte thoracique/traumatismes , Aorte thoracique/chirurgie , Technique de Western , Pression sanguine/physiologie , Chromatographie en phase liquide à haute performance , Endothélium vasculaire/traumatismes , Muscles lisses vasculaires/métabolisme , Curarisants dépolarisants/pharmacologie , Phényléphrine/pharmacologie , Potassium/pharmacologie , Protéine kinase C/métabolisme , Dosage radioimmunologique , Rat Wistar , /métabolisme , Vasoconstriction/effets des médicaments et des substances chimiques
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