<prompt> Nitric oxide is produced from?EndotheliumRBCPlateletsLymphocytes  <response>: ANSWER: A EndotheliumREF: Guytons physiology 22nd edition page 199Nitric oxide should not be confused with nitrous oxide N2O, an anesthetic and greenhouse gas, or with nitrogen dioxide NO2, a brown toxic gas and a major air pollutant.Nitric oxide, known as the endothelium-derived relaxing factor, or EDRF, is biosynthesized endogenously from L-arginine, oxygen and NAD PH by various nitric oxide synthase NOS enzymes. Reduction of inorganic nitrate may also serve to make nitric oxide. The endothelium inner lining of blood vessels uses nitric oxide to signal the surrounding smooth muscle to relax, thus resulting in vasodilation and increasing blood flow. 