Angiotensin-(1-7)-stimulated nitric oxide and superoxide release from endothelial cells

The stimulation of endothelium-dependent NO release by angiotensin-(1-7) [A ng-(1-7)] has been indirectly shown in terms of vasodilation, which was dim inished by NO synthase inhibition or removal of the endothelium, However, d irect measurement of endothelium-derived NO has not been analyzed, With a s elective porphyrinic microsensor, NO release was directly assessed from sin gle primary cultured bovine aortic endothelial cells. Ang-(1-7) caused a co ncentration-dependent release of NO of 1 to 10 mu mol/L, which was attenuat ed by NO synthase inhibition. [D-Ala(7)]Ang-(1-7) (5 mu mol/L), described a s a selective antagonist of Ang-(1-7) receptors, inhibited Ang-(1-7)-induce d NO release only by approximate to 50%, whereas preincubation of bovine ao rtic endothelial cells with the angiotensin II subtype 1 and 2 receptor ant agonists EXP 3174 and PD 123,177 (both at 0.1 mu mol/L) led to an inhibitio n of 60% and 90%, respectively. A complete blockade of the Ang-(l-7)-induce d NO release was observed on preincubation of the cells with 1 mu mol/L con centration of the bradykinin subtype 2 receptor antagonist icatibant (HOE 1 40), suggesting an important role of local kinins in the action of Ang-(1-7 ). Simultaneous direct measurement of superoxide (O-2(-)) detected by an O- 2(-)-sensitive microsensor revealed that the moderately Ang-(1-7)-stimulate d NO release was accompanied by a very slow concomitant O-2(-) production w ith a relative low peak concentration in comparison to the O-2(-) productio n of the strong NO releasers bradykinin and, especially, calcium ionophore, Thus, Ang-(1-7) might preserve the vascular system, among others, due to i ts low formation of cytotoxic peroxynitrite by the reaction between NO and O-2(-).