The complex trans-[RuCl([15]aneN4)NO]2+ induces rat aorta relaxation by ultraviolet light irradiation

The aim of the present study was to investigate the possible endogenous storage of photosensitive nitric oxide, and also to examine the relaxant effect of NO released from the compound by UV light irradiation. Aorta was isolated from rats and the endothelium was mechanically removed. Denuded aortic rings pre-contracted with prostaglandin F2α responded with relaxation to UV light irradiation. The first stimulation produced the greatest response that decreased until complete disappearance. After this, the addition of the compound in the absence of light did not produce any response. However, in the presence of UV light irradiation, the complex trans-[RuCl([15]aneN4)NO]2+ induced 100% relaxation. After incubation with the nitric oxide scavenger, oxyhaemoglobin, this relaxation was completely abolished. In PGF22α-pre-contracted aortas, the time to reach maximum relaxation was only 50 s. Taken together, these results suggest that preformed endogenous nitric oxide stores exist in the denuded rat aorta, and that they are sensitive to UV light. The photoinduction of the complex trans-[RuCl([15]aneN4)NO]2+ induces complete aorta relaxation, which is due to release of nitric oxide in the extracellular medium.