Pharmacological Characterization of the Vasodilating Effect Induced by the Ruthenium Complex Cis-[Ru(No)(No2) (bpy)(2)]center Dot(Pf6)(2)

Nitric oxide (NO) can be found in different species and is a potent vasodilator. The ruthenium compound cis-[Ru(NO)(NO2) (bpy)(2)]center dot(PF6)(2) (BPY) can generate NO. This study aimed to investigate the BPY stability at physiological pH, the cellular mechanisms involved in BPY effect, NO species originating from BPY, and to verify how BPY affects blood pressure. Our results has shown that at pH 7.4 and 9.4, the NO coordinated to ruthenium (Ru-NO) is converted to nitrite (Ru-NO2-) and remains stable. In aortic rings, the stable configuration of BPY (Ru-NO2-) induces vascular relaxation in a concentration-dependent manner. Thus, further experiments were made with stable configuration of BPY (Ru-NO2-). The relaxation induced by BPY was abolished in the presence of guanylyl cyclase inhibitor and decreased in the presence of potassium channel blocker. By using radicalar (NO center dot) and nitroxyl (NO-) scavenger, our results suggest that the BPY mainly release the radicalar species. By using fluorescence probes to detect intracellular NO concentration ([NO](i)) and cytosolic Ca2+ concentration ([Ca2+](c)), we verified that in smooth muscle cells, BPY induces an increase in [NO](i) and a decrease in [Ca2+](c). The intravenous bolus injection of 1.25, 2.5, and 5.0 mg/kg from stable configuration of BPY results in a decrease on basal blood pressure values. Taken together, our results indicated that the stable configuration of the compound BPY induces vascular relaxation in aorta because of NO release and decrease of [Ca2+] c in vascular smooth muscle cells. Also, the stable configuration is able to reduce the blood pressure in a dose-dependent manner.