NOS3 and endothelial dysfunction: In favour of those vasoreactivity effects, the production and bioavailability of the soluble gas nitric oxide (NO) obtained from the L-arginine aminoacidic substrate plus oxygen and cofactors [e.g., reduced nicotinamide adenine dinucleotide phosphate (NADPH), tetrahydrobiopterin (BH4), flavin mononucleotide (FMN), flavin adenine dinucleotide/mononucleotide (FAD), and iron protoporphyrin IX (heme)] are synthesised in L-citrulline and NO by the endothelial nitric oxide synthase (eNOS) isoform playing a central role in the pathogenesis of endothelial dysfunction.