The effects of ruthenium tetraammine compounds on vascular smooth muscle

Abstract

The time course of the relaxation effect induced by a single dose (3 x 10(-6) mol/L) of trans-[Ru(NH(3))(4)L(NO)](3+) (L = nic, 4-pic, py, imN, P(OEt)(3), SO(3)(2-), NH(3), and pz) species and sodium nitroprusside (4 x 10(-9) mol/L) was studied in aortic rings without endothelium and pre-contracted with noradrenaline (1 x 10(-6) mol/L). All the compounds induced a relaxing effect in the aortic rings, but the intensity and time of relaxation were different. Only the species where L = py, 4-pic, and P(OEt)(3) were able to induce 100% (99-100%) of the relaxing effect during the assay. trans-[Ru(NH(3))(4)(L)(NO)](3+) (L = SO(3)(2-) and NH(3)) showed the lowest relaxing effect (36 and 37%, respectively) when compared with the other compounds. Relationship was observed between the time corresponding to half of the maximum relaxation intensity observed and, respectively, k(-NO), E([Ru(NO)])(/[Ru(NO)])(0')(3+)(2+') in trans-[Ru(NH(3))(4)(L)(NO)](3+) species and E(Ru(III)/Ru(II))(0') in trans- [Ru(NH(3))(4)(L)(H(2)O)](3+) ions. These relationships strongly suggested that the NO liberation from the reduced nitrosyl complexes was responsible for the observed relaxation. (c) 2006 Elsevier Inc. All rights reserved.