title: Is reduction of the sulfonated tetrazolium 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2-tetrazolium 5-carboxanilide a reliable measure of intracellular superoxide production?
abstract: The sulfonated tetrazolium 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2-tetrazolium 5-carboxanilide (XTT) is advantageous in that it yields a water-soluble formazan, unlike most other available tetrazoliums. XTT is reducible by superoxide, as are other tetrazoliums, but is not directly reduced by xanthine oxidase plus xanthine or by glucose oxidase plus glucose. This led to the suggestion that XTT reduction might serve as a reliable index of intracellular O(2)(-) production. We now show that soluble extracts of Escherichia coli contain two NADPH:XTT reductases that act aerobically or anaerobically. That being the case, XTT reduction is not a reliable measure of intracellular O(2)(-).
authors.affiliation: The Department of Biochemistry, Faculty of Medicine, Kuwait University, P O Box 24923, 13110, Safat, Kuwait. lbenov@hsc.kuniv.edu.kw
authors.forename: Ludmil
authors.initials: L
authors.lastname: Benov
authors.forename: Irwin
authors.initials: I
authors.lastname: Fridovich
mesh_terms: D002374:Catalase / Q000494:pharmacology; D004098:Dihydroxyacetone / Q000378:metabolism; D004926:Escherichia coli / Q000145:classification / Q000201:enzymology; D005985:Glyceraldehyde / Q000378:metabolism; D007202:Indicators and Reagents; D009243:NAD / Q000378:metabolism; D009246:NADH Tetrazolium Reductase / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000032:analysis* / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D007202:Indicators and Reagents; D013778:Tetrazolium Salts; D009243:NAD; D013481:Superoxides; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide; D005985:Glyceraldehyde; D009249:NADP; D002374:Catalase; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D009246:NADH Tetrazolium Reductase; D004098:Dihydroxyacetone