FIGURE 1.

The nitric oxide (NO) pathway including involved substrates, enzymes and downstream pathway. l-arginine amino acid is the substrate from which NO is generated by the enzyme NOS. Three different NOS-isoforms exist: neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible (inflammatory) NOS (iNOS). In addition, several exogenous substrates exist to induce the NO-downstream pathway. l-NAME and LNMMA block NOS function. The biological functions of NO are related to the activation of sGC; subsequently influencing cGMP. NOS, Nitric oxide synthase; l-NAME, N(ω)-nitro-l-arginine methyl ester; LNMMA, L-N(G)-monomethyl arginine; sGC, Soluble guanylyl cyclase; cGMP, Cyclic guanosine monophosphate.