The endogenous production of nitric oxide (NO) plays a key role in many bioregulatory systems, including the control of vascular tone, inhibition of platelet aggregation, neurotransmission, and macrophage toxicity. Many of these pathways are activated by the stimulation of soluble guanylyl cyclase (1 ). Owing to the inconvenient handling of solutions of NO, there is an increased interest in compounds capable of generating NO in situ . These compounds can be divided into different groups that include organic nitrates [e.g., glyceryl trinitrate (GTN)], organic nitrites (e.g., iso amyl nitrite), inorganic nitroso compounds [e.g., sodium nitroprusside (SNP)], sydnonimines [e.g., molsidomine (SIN-1)], and S-nitrosothiols (RSNO) [e.g., S-nitrosoglutathione, (GSNO)]. All these compounds differ in their need for specific cofactors required to release NO (2 ).