Cu-metallothioneins (Cu(I)8-MTs) in LEC rat livers 13 weeks after birth still act as antioxidants.
Redox properties of metallothioneins (MTs) and Cu in the cytosol from Long-Evans Cinnamon (LEC) rat livers 13 weeks after birth were investigated. MTs from LEC rat livers contain 8 g atoms of Cu and 1 g atom of Zn per mole of protein (Cu(I)8-MTs). Titration of Cu(I)8-MTs with CuCl2 indicates that Cu(I)8-MTs were able to reduce further 2-g atoms of cupric ions per mole MTs as bound form. Hg2+-induced hydroxyl radical generation from Cu(I)8-MTs was demonstrated by ESR using the spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The intensity of DMPO-OH signal from Cu-loaded MTs was increased with the increasing number of Cu in MTs. The used cytosol fraction contained 1.37 mM total Cu and 5 mM DTNB titrable-SH groups has a potential to reduce 2 mM CuCl2. No ESR signal due to Cu2+ was also detected with LEC rat liver cytosol, whereas strong Cu2+ signal appeared by the addition of HgCl2. The rate constants for the reaction of Cu(I)8-MTs with superoxide and hydroxyl radicals were estimated to be 2 x 10(6) and > or = 10(12) M(-1)s(-1), respectively, from competition kinetics. Cu2+-catalyzed oxidation of DNA was strongly inhibited both in the presence of Cu-unsaturated MTs and GSH. The results suggest that Cu(I)8-MTs from LEC rat livers just before hepatitis still act as antioxidants.
Shishido
N
N
Department of Chemistry, Asahikawa Medical College, Japan.
Nakayama
K
K
Takazawa
A
A
Ohyama
T
T
Nakamura
M
M
D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive / Q000187:drug effects; D019256:Cadmium Chloride / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D003497:Cyclic N-Oxides / Q000737:chemistry; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D005978:Glutathione / Q000378:metabolism; D006527:Hepatolenticular Degeneration / Q000201:enzymology*; D017665:Hydroxyl Radical / Q000032:analysis / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology; D008668:Metallothionein / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D051381:Rats; D020332:Rats, Inbred LEC; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
D000975:Antioxidants; D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; C007121:copper thionein; D017665:Hydroxyl Radical; D008627:Mercuric Chloride; C069977:2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy; D003300:Copper; D004247:DNA; D008668:Metallothionein; D013482:Superoxide Dismutase; D005978:Glutathione; D019256:Cadmium Chloride; C029892:cupric chloride