title: Nitric oxide formation from hydroxylamine by myoglobin and hydrogen peroxide.
abstract: Hydroxylamine (HA), which is a natural product of mammalian cells, has been shown to possess vasodilatory properties in several model systems. In this study, HA and methyl-substituted hydroxylamines, N-methylhydroxylamine (NMHA) and N,N-dimethylhydroxylamine (NDMHA), have been tested for their ability to generate free diffusible nitric oxide (NO) in the presence of myoglobin (Mb) and hydrogen peroxide. A NO-specific conversion of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO) to 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (carboxy-PTI), measured by electron spin resonance (ESR) spectroscopy, along with nitrite and nitrate production, was observed for HA but not for NMHA and NDMHA. ESR measurements at 77 K showed the formation of the ferrous nitrosyl myoglobin, Mb-NO, in the reaction mixtures containing Mb, H2O2 and HA. Our data also demonstrate that Mb-NO is an end product of the reaction pathway involving Mb, H2O2 and HA, rather than a reaction intermediate in the formation of NO. In summary, our results demonstrate a possible pathway of NO formation from HA, however, the significance of this mechanism for bioactivation of HA in vivo is unknown at the present time.
authors.affiliation: Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. sono@helix.nih.gov
authors.forename: J
authors.initials: J
authors.lastname: Taira
authors.forename: V
authors.initials: V
authors.lastname: Misík
authors.forename: P
authors.initials: P
authors.lastname: Riesz
mesh_terms: D000818:Animals; D004123:Dimethylamines / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006736:Horses; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019811:Hydroxylamine / Q000378:metabolism*; D006898:Hydroxylamines / Q000378:metabolism; D007700:Kinetics; D009211:Myoglobin / Q000378:metabolism*; D009566:Nitrates / Q000032:analysis; D009569:Nitric Oxide; D009573:Nitrites / Q000032:analysis
chemical_list: D004123:Dimethylamines; D006898:Hydroxylamines; D009211:Myoglobin; D009566:Nitrates; D009573:Nitrites; D019811:Hydroxylamine; D009569:Nitric Oxide; C063231:N,N-dimethylhydroxylamine; D006861:Hydrogen Peroxide; C018338:N-methylhydroxylamine