MANGANESE POTENTIATION OF NITRIC OXIDE-MEDIATED VASCULAR RELAXATION

The half-life of nitric oxide (NO) and the relaxation of aortic rings are enhanced by superoxide dismutase. Manganese and manganese-containi ng preparations have been reported to mimic superoxide dismutase activ ity. In the current study, manganese was tested for its ability to pot entiate the activity of NO both in vitro and in vivo. Manganese relaxa tion of aortic segments was endothelium dependent as well as concentra tion dependent. Cyclic GMP concentrations in the segments were increas ed 2- and 4-fold with 5 and 300 mu M manganese, respectively. N-Monome thyl-L-arginine pretreatment of aortic rings abolished the relaxation and cyclic GMP accumulation mediated by manganese. Infusion of mangane se into conscious, restrained rats resulted in a decrease of blood pre ssure which was abolished by N-nitro-L-arginine pretreatment. Therefor e, manganese may prolong the half-life of NO by a mechanism that mimic s the action of superoxide dismutase resulting in potentiation of NO a ctions in vascular tissue.