title: Electron paramagnetic resonance study on free radical scavenging and/or generating activity of dopamine-4-O-sulfate.
abstract: The free radical scavenging and/or generating activity of dopamine-4-O-sulfate was examined and compared with that of dopamine. In humans, dopamine mostly exists in two isomeric forms of sulfate ester conjugates as metabolites; i.e., dopamine-3-O-sulfate and dopamine-4-O-sulfate in the circulation. Dopamine is generally believed to be oxidized by molecular oxygen or another reactive oxygen species under physiological conditions, to form oxidized dopamine derivatives that are cytotoxic. However, it is not known whether dopamine conjugates are generated on interaction with reactive oxygen species or not. In the present study, we measured the susceptibility to oxidization of dopamine-4-O-sulfate by using electron paramagnetic resonance (EPR) spectroscopy and optical absorption spectrometry. Dopamine was easily oxidized and dopamine-derived radicals appeared, whereas dopamine-4-O-sulfate was not oxidized under physiological conditions. Furthermore, dopamine-4-O-sulfate did not react with a strong oxidizing agent, sodium periodate. These results suggest that dopamine-4-O-sulfate has resistance against autoxidation, and seems to be a stable metabolite of dopamine.
authors.affiliation: Department of Pharmacology, The University of Tokushima School of Medicine, Japan. kirima@basic.med.tokushima-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Kirima
authors.forename: K
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: M
authors.initials: M
authors.lastname: Yoshizumi
authors.forename: T
authors.initials: T
authors.lastname: Kameda
authors.forename: H
authors.initials: H
authors.lastname: Houchi
authors.forename: M
authors.initials: M
authors.lastname: Azuma
authors.forename: T
authors.initials: T
authors.lastname: Tamaki
mesh_terms: D004298:Dopamine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology* / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology*; D005609:Free Radicals / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D010504:Periodic Acid / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013481:Superoxides / Q000737:chemistry; D014466:Ultraviolet Rays; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D010504:Periodic Acid; D013481:Superoxides; D017665:Hydroxyl Radical; C022807:dopamine 4-O-sulfate; D006735:Horseradish Peroxidase; D014969:Xanthine Oxidase; D004298:Dopamine