title: Identification of radicals formed in the reaction mixtures of rat liver microsomes with ADP, Fe3+ and NADPH using HPLC EPR and HPLC EPR MS.
abstract: The reaction of rat liver microsomes with Fe(3+), ADP and NADPH was examined using EPR, HPLC-EPR and HPLC-EPR-MS combined use of spin trapping technique. A prominent EPR spectrum (alpha(N) = 1.58 mT and alpha(H)beta = 0.26 mT) was observed in the complete reaction mixture. The EPR spectrum was hardly observed for the complete reaction mixture without rat liver microsomes. The radicals appear to be derived from microsomal components. The EPR spectrum was also hardly observed in the absence of Fe(3+). Addition of some iron chelators such as EDTA, citrate and ADP resulted in the dramatic change in the EPR intensity. Iron ions seem to be essential for this reaction. For the complete reaction mixture with boiled microsomes, a weak EPR spectrum was observed, suggesting that enzymes participate in the reaction. Five peaks were separated on the HPLC-EPR elution profile of the complete reaction mixture of rat liver microsomes with ADP, Fe(3+) and NADPH. The retention times of the peaks 1 to 5 were 19.4, 22.5, 27.3, 29.8 and 31.4 min, respectively. To identify the radical adducts, HPLC-EPR-MS analyses were performed for the three prominent peaks. The HPLC-EPR-MS analyses showed that a new radical adduct, 4-POBN/1-hydroxypentyl radical, in addition to 4-POBN/ethyl radical adducts, forms in a reaction mixture of rat liver microsomes with ADP, Fe(3+) and NADPH.
authors.affiliation: Department of Chemistry, Wakayama Medical University, 811-1 Kimiidera, Wakayama 641-8509, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Minakata
authors.forename: Etsuo
authors.initials: E
authors.lastname: Okuno
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakamura
authors.forename: Hideo
authors.initials: H
authors.lastname: Iwahashi
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D005609:Free Radicals / Q000032:analysis*; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000737:chemistry* / Q000378:metabolism; D009249:NADP / Q000737:chemistry* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005290:Ferric Compounds; D005609:Free Radicals; D009249:NADP; D000244:Adenosine Diphosphate