Fig. 1.
Upper panel: The expression of eNOS in the endothelium of the vessels decreases along the vascular tree, while blood cell eNOS carried by all main blood populations is equally distributed. Middle panel: In the blood compartment a circulating pool of NO metabolites is formed and transported in plasma and RBC. Bottom panel: NO can be synthesized enzymatically from L-arginine under normoxic conditions in a reaction catalyzed by a NOS, and under hypoxic conditions from nitrite by the nitrate reductase activity of proteins including deoxyhemoglobin (deoxyHb), deoxymyoglobin (deoxyMb), xantine oxidoreductase (XOR), carbonic anydrase (CA), and cytochrome C (cytC)/cytC-oxidase. eNOS, endothelial nitric oxide synthase; LNO2, nitrated lipids; RSNO, nitrosothiols; RNNO, nitrosamines.