Vascular Response Of Ruthenium Tetraamines In Aortic Ring From Normotensive Rats.

Background: Ruthenium (Ru) tetraamines are being increasingly used as nitric oxide (NO) carriers. In this context, pharmacological studies have become highly relevant to better understand the mechanism of action involved. Objective: To evaluate the vascular response of the tetraamines trans-[RuII(NH3)4(Py)(NO)]3+, trans-[RuII(Cl)(NO) (cyclan)](PF6)2, and trans-[RuII(NH3)4(4-acPy)(NO)]3+. Methods: Aortic rings were contracted with noradrenaline (10-6 M). After voltage stabilization, a single concentration (10-6 M) of the compounds was added to the assay medium. The responses were recorded during 120 min. Vascular integrity was assessed functionally using acetylcholine at 10-6 M and sodium nitroprusside at 10-6 M as well as by histological examination. Results: Histological analysis confirmed the presence or absence of endothelial cells in those tissues. All tetraamine complexes altered the contractile response induced by norepinephrine, resulting in increased tone followed by relaxation. In rings with endothelium, the inhibition of endothelial NO caused a reduction of the contractile effect caused by pyridine NO. No significant responses were observed in rings with endothelium after treatment with cyclan NO. In contrast, in rings without endothelium, the inhibition of guanylate cyclase significantly reduced the contractile response caused by the pyridine NO and cyclan NO complexes, and both complexes caused a relaxing effect. Conclusion: The results indicate that the vascular effect of the evaluated complexes involved a decrease in the vascular tone induced by norepinephrine (10-6 M) at the end of the incubation period in aortic rings with and without endothelium, indicating the slow release of NO from these complexes and suggesting that the ligands promoted chemical stability to the molecule. Moreover, we demonstrated that the association of Ru with NO is more stable when the ligands pyridine and cyclan are used in the formulation of the compound.Fundamento: As tetra-aminas de rutênio cada vez mais se destacam como carreadoras da molécula de óxido nítrico. Desse modo, estudos farmacológicos tornam-se altamente relevantes, afim de melhor compreender o mecanismo de ação envolvido. Objetivo: Avaliar a resposta vascular das tetra-aminas trans-[RuII(NH3)4(Py)(NO)]3+, trans-[RuII(Cl)(NO)(Cyclan)](PF6)2 e trans-[RuII(NH3)4(4-acPy)(NO)]3+. Métodos: Anéis de aorta foram pré-contraídos com noradrenalina (10-6M). Após estabilização da tensão, concentração única (10-6M) dos compostos foi adicionada ao banho de incubação. As respostas foram registradas ao longo de 120 minutos. A integridade vascular foi avaliada funcionalmente (acetilcolina 10-6M; nitroprussiato de sódio 10-6M) e histologicamente Resultados: A análise histológica confirmou a presença ou não de células endoteliais nos tecidos analisados. Todos os complexos alteraram a resposta contrátil induzida pela noradrenalina, resultando em aumento de tônus seguido de efeito relaxante. Em anéis com endotélio, a inibição do óxido nítrico endotelial causou redução do efeito contrátil da piridina óxido nítrico. Não foram observadas respostas significativas em anéis com endotélio referente ao composto cyclan óxido nítrico. Por outro lado, em anéis sem endotélio, a inibição da guanilato ciclase reduziu significativamente a resposta contrátil dos complexos piridina óxido nítrico e cyclan óxido nítrico, levando ambos os compostos a um efeito relaxante. Conclusão: Os resultados obtidos demonstram que o efeito vascular dos complexos avaliados apresentaram diminuição no tônus vascular induzido pela noradrenalina (10-6M) ao final do tempo de incubação, em anéis com e sem endotélio, indicando liberação lenta da molécula de óxido nítrico do composto estudado e sugerindo que os ligantes causaram estabilidade química à molécula. Demonstramos que a ligação rutênio óxido nítrico é mais estável quando utilizamos os ligantes piridina e cyclan para a formulação do composto.

Enhanced Endothelium-dependent Relaxation Of Rat Pulmonary Artery Following β-adrenergic Overstimulation: Involvement Of The No/cgmp/vasp Pathway.

The aim of this study was to investigate whether β-adrenoceptor (β-AR) overstimulation induced by in vivo treatment with isoproterenol (ISO) alters vascular reactivity and nitric oxide (NO) production and signaling in pulmonary arteries. Vehicle or ISO (0.3mgkg(-1)day(-1)) was administered daily to male Wistar rats. After 7days, the jugular vein was cannulated to assess right ventricular (RV) systolic pressure (SP) and end diastolic pressure (EDP). The extralobar pulmonary arteries were isolated to evaluate the relaxation responses, protein expression (Western blot), NO production (diaminofluorescein-2 fluorescence), and cyclic guanosine 3',5'-monophosphate (cGMP) levels (enzyme immunoassay kit). ISO treatment induced RV hypertrophy; however, no differences in RV-SP and EDP were observed. The pulmonary arteries from the ISO-treated group showed enhanced relaxation to acetylcholine that was abolished by the NO synthase (NOS) inhibitor N(ω)-nitro-l-arginine methyl ester (l-NAME); whereas relaxation elicited by sodium nitroprusside, ISO, metaproterenol, mirabegron, or KCl was not affected by ISO treatment. ISO-treated rats displayed enhanced endothelial NOS (eNOS) and vasodilator-stimulated phosphoprotein (VASP) expression in the pulmonary arteries, while phosphodiesterase-5 protein expression decreased. ISO treatment increased NO and cGMP levels and did not induce eNOS uncoupling. The present data indicate that β-AR overactivation enhances the endothelium-dependent relaxation of pulmonary arteries. This effect was linked to an increase in eNOS-derived NO production, cGMP formation and VASP content and to a decrease in phosphodiesterase-5 expression. Therefore, elevated NO bioactivity through cGMP/VASP signaling could represent a protective mechanism of β-AR overactivation on pulmonary circulation.