Current concepts on the role of nitric oxide in portal hypertension

Figure 1 Nitric oxide formation and function. Nitric oxide synthase (NOS) catalyzes the biosynthesis of nitric oxide (NO) from L-arginine, nicotinamide adenine dinucleotide phosphate (NADPH) and O₂•NO freely diffuses into cells where it mediates vascular relaxation by stimulating the cyclic guanosine 3’-5’-monophosphate (cGMP)/cGMP-dependent protein kinase G (PKG) pathway. It also forms reactive nitrogen species (RNS) which leads to many damaging reactions including lipid peroxidation and DNA strand breaks. GTP: Guanosine 5’-triphosphate; sGC: Soluble guanylyl cyclase.