Dioxygen-dependent metabolism of nitric oxide in mammalian cells.
Steady-state gradients of NO within tissues and cells are controlled by rates of NO synthesis, diffusion, and decomposition. Mammalian cells and tissues actively decompose NO. Of several cell lines examined, the human colon CaCo-2 cell produces the most robust NO consumption activity. Cellular NO metabolism is mostly O2-dependent, produces near stoichiometric NO3-, and is inhibited by the heme poisons CN-, CO (K(I) approximately 3 microM), phenylhydrazine, and NO and the flavoenzyme inhibitor diphenylene iodonium. NO consumption is saturable by O2 and NO and shows apparent K(M) values for O2 and NO of 17 and 0.2 microM, respectively. Mitochondrial respiration, O2*-, and H2O2 are neither sufficient nor necessary for O2-dependent NO metabolism by cells. The existence of an efficient mammalian heme and flavin-dependent NO dioxygenase is suggested. NO dioxygenation protects the NO-sensitive aconitases, cytochrome c oxidase, and cellular respiration from inhibition, and may serve a dual function in cells by limiting NO toxicity and by spatially coupling NO and O2 gradients.
Gardner
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PR
Division of Critical Care Medicine, Children's Hospital Medical Center, Cincinnati, OH, USA. gardp0@chmcc.org
Martin
L A
LA
Hall
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D
Gardner
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AM
D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors; D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology; D002460:Cell Line; D002474:Cell-Free System; D003486:Cyanides / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology; D010105:Oxygenases / Q000378:metabolism; D051381:Rats; D013481:Superoxides / Q000378:metabolism
D003486:Cyanides; D005609:Free Radicals; D009566:Nitrates; D013481:Superoxides; D009569:Nitric Oxide; D002248:Carbon Monoxide; D006861:Hydrogen Peroxide; D010105:Oxygenases; C114415:nitric oxide dioxygenase; D000154:Aconitate Hydratase; D010100:Oxygen