Hoe 140 (d‐Arg‐[Hyp3, Thi5, d‐Tic7, Oic8]bradykinin) is a new bradykinin (BK)‐antagonist. It was tested in several in vitro assays and compared with d‐Arg‐[Hyp2, Thi5,8,d‐Phe7]BK. In receptor binding studies in guinea‐pig ileum preparations, Hoe 140 showed an IC50 of 1.07 × 10−9mol l−1 and a KI value of 7.98 × 10−10 mol l−1. In isolated organ preparations Hoe 140 and d‐Arg‐[Hyp2, Thi5,8, d‐Phe7]BK inhibited bradykinin‐induced contractions concentration dependently, with IC50‐values in the guinea‐pig ileum preparation of 1.1 × 10−8 mol l−1 and 3 × 10−5 mol l−1, respectively. pA2 values in this tissue were 8.42 and 6.18, respectively. In the rat uterus preparation the IC50 value was 4.9 × 10−9 mol l−1 for Hoe 140. d‐Arg‐[Hyp2, Thi5,8, d‐Phe7]BK showed an IC50 of 4.0 × 10−6 mol l−1. The IC50 values in the guinea‐pig isolated pulmonary artery were 5.4 × 10−9 mol l−1 and 6.4 × 10−6 mol l−1, respectively. In the rabbit aorta no inhibitory effects on Des‐Arg9‐BK induced contractions were observed. In cultured bovine endothelial cells, Hoe 140 antagonized (IC50 = 10−8 mol l−1) bradykinin‐induced endothelium‐derived relaxing factor (EDRF) release and the bradykinin‐induced increase in cytosolic free calcium (IC50 = 10−9 mol l−1). Hoe 140 (10−7 mol l−1) totally suppressed the bradykinin‐induced (10−8 to 10−4mol l−1) prostacyclin (PGI2) release from cultured endothelial cells of bovine aorta. d‐Arg‐[Hyp2, Thi5,8, d‐Phe7]BK (10−7 mol l−1) showed a weaker antagonism. Taken together these results show that Hoe 140 is a highly potent bradykinin antagonist. It was two to three orders of magnitude more potent than d‐Arg‐[Hyp2, Thi5,8, d‐Phe7]BK.

Abstract-The stimulation of endothelium-dependent NO release by angiotensin-(1-7) ] has been indirectly shown in terms of vasodilation, which was diminished by NO synthase inhibition or removal of the endothelium. However, direct measurement of endothelium-derived NO has not been analyzed. With a selective porphyrinic microsensor, NO release was directly assessed from single primary cultured bovine aortic endothelial cells. Ang-(1-7) caused a concentration-dependent release of NO of 1 to 10 mol/L, which was attenuated by NO synthase inhibition.[D-Ala 7 ]Ang-(1-7) (5 mol/L), described as a selective antagonist of Ang-(1-7) receptors, inhibited Ang-(1-7)-induced NO release only by Ϸ50%, whereas preincubation of bovine aortic endothelial cells with the angiotensin II subtype 1 and 2 receptor antagonists EXP 3174 and PD 123,177 (both at 0.1 mol/L) led to an inhibition of 60% and 90%, respectively. A complete blockade of the Ang-(1-7)-induced NO release was observed on preincubation of the cells with 1 mol/L concentration of the bradykinin subtype 2 receptor antagonist icatibant (HOE 140), suggesting an important role of local kinins in the action of Ang-(1-7). Simultaneous direct measurement of superoxide (O 2 Ϫ ) detected by an O 2 Ϫ -sensitive microsensor revealed that the moderately Ang-(1-7)-stimulated NO release was accompanied by a very slow concomitant O 2 Ϫ production with a relative low peak concentration in comparison to the O 2 Ϫ production of the strong NO releasers bradykinin and, especially, calcium ionophore. Thus, Ang-(1-7) might preserve the vascular system, among others, due to its low formation of cytotoxic peroxynitrite by the reaction between NO and O 2 Ϫ . (Hypertension. 2001;37:72-76.)

Abstract-Recently, we demonstrated that the heptapeptide angiotensin-(1-7) (Ang- [1][2][3][4][5][6][7]) exhibits a favorable kinetic of nitric oxide (NO) release accompanied by extremely low superoxide (O 2 Ϫ ) production. In this report we describe AVE 0991, a novel nonpeptide compound that evoked effects similar to Ang-(1-7) on the endothelium. AVE 0991 and unlabeled Ang-(1-7) competed for high-affinity binding of [125 I]-Ang-(1-7) to bovine aortic endothelial cell membranes with IC 50 values of 21Ϯ35 and 220Ϯ280 nmol/L, respectively. Stimulated NO and O 2 Ϫ release from bovine aortic endothelial cells was directly and simultaneously measured on the cell surface by selective electrochemical nanosensors. Peak concentrations of NO and O 2 Ϫ release by AVE 0991 and Ang-(1-7) (both 10 mol/L) were not significantly different (NO: 295Ϯ20 and 270Ϯ25 nmol/L; O 2 Ϫ : 18Ϯ2 and 20Ϯ4 nmol/L). However, the released amount of bioactive NO was Ϸ5 times higher for AVE 0991 in comparison to Ang-(1-7). The selective Ang-(1-7) antagonist [D-Ala 7 ]-Ang-(1-7) inhibited the AVE 0991-induced NO and O 2 Ϫ production by Ϸ50%. A similar inhibition level was observed for the Ang II AT 1 receptor antagonist EXP 3174. In contrast, the Ang II AT 2 receptor antagonist PD 123,177 inhibited the AVE 0991-stimulated NO production by Ϸ90% but without any inhibitory effect on O 2 Ϫ production. Both NO and O 2 Ϫ production were inhibited by NO synthase inhibition (Ϸ70%) and by bradykinin B 2 receptor blockade (Ϸ80%). AVE 0991 efficiently mimics the effects of Ang-(1-7) on the endothelium, most probably through stimulation of a specific, endothelial Ang-(1-7)-sensitive binding site causing kinin-mediated activation of endothelial NO synthase.

We investigated the effects of aortic banding-induced hypertension on the endothelium-dependent vasodilator responses in the aorta and coronary circulation of Sprague-Dawley rats. We studied the influence of hypertension on the endothelial nitric oxide synthase (NOS III) expression, assessed by Western blot and reverse transcription-polymerase chain reactions experiments, and on the superoxide anion (O2-) production. Two weeks after aortic banding, the endothelium-dependent relaxations were not altered. At this time, the expression of NOS III in the aorta and in confluent coronary microvascular endothelial cells (RCMECs) exhibited no marked changes, whereas O2- production was enhanced 1.9-fold in aortas from aortic-banded rats. Six weeks after aortic banding, the endothelium-dependent dilations were markedly impaired in the heart (50% decrease) and aorta (35% decrease). Analysis of NOS III protein and mRNA levels revealed marked increases in both aortas and confluent RCMECs (2.6- to 4-fold) from aortic-banded compared with sham-operated rats. There was no further increase in O2production in both the aorta and confluent RCMECs from aortic-banded rats. An enhanced nitrotyrosine protein level was also detected in the aorta from 6-week aortic-banded rats. These findings indicate that in hypertension induced by aortic banding, an enhanced O2- production alone is not sufficient to produce endothelial dysfunction. Endothelial vasodilator hyporesponsiveness was observed only when NOS III expression and O2- production were increased and was associated with the appearance of enhanced nitrotyrosine residues. This would suggest that the development of endothelial dysfunction is linked to an overproduction of not one, but two, endothelium-derived radicals that might lead to the formation of peroxynitrite.

We studied whether inhibition of angiotensin converting enzyme stimulates the formation of nitric oxide and prostacyclin in cultured human and bovine endothelial cells by an enhanced accumulation of endothelium-derived bradykinin. Nitric oxide formation was assessed in terms of intracellular cyclic GMP accumulation, prostacyclin release by a specific radioimmunoassay. Inhibition of angiotensin converting enzyme by ramiprilat dose-and time-dependently increased the formation of nitric oxide and prostacyclin. These increases, peaking within 10 minutes, were maintained for at least 60 minutes. 1 Although the primary action of these agents is the inhibition of systemic and local formation of angiotensin II, a number of experimental and clinical data suggest that other dilator mechanisms may be involved in the hypotensive effect of ACE inhibitors. 2 -3 Since ACE is identical to the kininase II of the kallikrein-kinin system that inactivates bradykinin by liberating the C-terminal dipeptide phenylalanyl-arginine, 4 it has been suspected that a significant part of the blood pressure-lowering effect of ACE inhibitors in vivo is

No abstract

These results demonstrate that NOS III expression in different tissues is differentially affected by hypertension. Moreover, although an elevated superoxide anion production is apparent in the aorta, a reduced soluble guanylyl cyclase expression appears to account for the observed vasodilator dysfunction in SHR.

No abstract