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. 2010 Aug 16;31(9):1095–1102. doi: 10.1038/aps.2010.127

Figure 3.

Figure 3

Formation of oxygen-derived free radicals of relevance for endothelium-dependent responses, and pharmacological agents commonly used to determine their importance. Superoxide anions (O2−) can be generated from molecular oxygen by the actions of various enzymes. O2− can react with NO to form peroxynitrite (ONOO−). It can also be converted to hydrogen peroxide (H2O2) by superoxide dismutase (SOD). H2O2 can be transformed to hydroxyl radicals by ferrous ions or converted to H2O by catalase and glutathione. Tiron scavenges O2− inside cells. DETCA inhibits SOD. Deferoxamine is an iron chelator that scavenges hydroxyl radicals. L-NAME inhibits NO synthase. MnTMPyP mimics the combined effect of SOD and catalase. DETCA=diethyldithiocarbamic acid; GSH=glutathione; GSSG=glutathione disulphide; L-NAME=Nω-nitro-L-arginine methyl ester hydrochloride; MnTMPyP=Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride; NO=nitric oxide; tiron=4,5-dihydroxy-1,3-benzenedisulphonic acid. (Adapted from Shi et al 2007, by permission)Arachidonic acid is converted to endoperoxides by the activity of cyclooxygenase (COX). Endoperoxides are then converted to various prostaglandins by their respective synthase.