Oxidation of N-hydroxyguanidine by nitric oxide and the possible generation of vasoactive species.

It has been reported previously that the N-hydroxyguanidine function of N-hydroxy-L-arginine can react with nitric oxide (NO) to generate other species that can act as potent vasodilators with different biological lifetimes than NO. The identities of these species have yet to be determined. Therefore, we have studied the reaction between NO and N-hydroxyguanidine and determined that N-hydroxyguanidine is capable of reducing NO to yield nitrous oxide (N2O) and possibly other nitroso species. It is likely that at least some of the N2O formation in these reactions is due to the initial generation of nitroxyl (HNO). Since HNO has been shown to be a potent vasorelaxant, it is possible that some of the non-NO-mediated biological activity alluded to in previous studies was due to HNO and that other nitroso-species generated in the reaction may also contribute to the overall pharmacological activity by release of either NO or HNO.