Fig. 1.

Schematic presentation of nitric oxide (NO) generation and metabolism in the body. NO is generated from the classical nitric oxide synthase (NOS)-l-arginine pathway and from the reduction of systemic nitrate (${\text{NO}}_3^{-}$) and nitrite (${\text{NO}}_2^{-}$). Systemic ${\text{NO}}_3^{-}\text{ and }{\text{NO}}_2^{-}$ originates from the oxidation of NO in biological fluids and from the diet. ${\text{NO}}_3^{-}$ undergoes reduction to ${\text{NO}}_2^{-}$ and then to NO. Possible ${\text{NO}}_3^{-}\text{ and }{\text{NO}}_2^{-}$ reduction pathways to NO in the body are depicted