Reduction of the metallochromic indicators arsenazo III and antipyrylazo III to their free radical metabolites by cytoplasmic enzymes.
At a concentration much lower than that usually employed for measuring cytosolic ionized Ca2+ concentrations, arsenazo III underwent a one-electron reduction by rat liver cytosolic fraction or a hypoxanthine-xanthine oxidase system to produce an azo anion radical metabolite. NADH, NADPH, N1-methylnicotinamide, hypoxanthine, and xanthine, in that order, could serve as a source of reducing equivalents for the production of this free radical by the cytosolic fraction. The steady-state concentration of the azo anion radical and the arsenazo III-stimulated O2 consumption were enhanced by calcium and magnesium. Antipyrylazo III was ineffective in increasing O2 consumption by rat liver cytosolic fraction and gave a much weaker ESR signal of an azo anion radical with both the liver cytosolic fraction, in the presence of NADH, and the hypoxanthine-xanthine oxidase system.
Moreno
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Mason
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Docampo
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R
D000818:Animals; D001150:Arsenazo III / Q000378:metabolism*; D001391:Azo Compounds / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D003593:Cytoplasm / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000378:metabolism; D008099:Liver / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009243:NAD / Q000378:metabolism; D009282:Naphthalenesulfonates / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D014969:Xanthine Oxidase / Q000378:metabolism
D001391:Azo Compounds; D005609:Free Radicals; D007042:Hypoxanthines; D009282:Naphthalenesulfonates; D009243:NAD; D001150:Arsenazo III; D019271:Hypoxanthine; D014969:Xanthine Oxidase; C016238:antipyrylazo III; D008274:Magnesium; D002118:Calcium