title: Oxidative damage of rat liver mitochondria during exposure to t-butyl hydroperoxide. Role of Ca²⁺ ions in oxidative processes.
abstract: OBJECTIVE
  The present study was designed for further evaluation of the biochemical mechanism of hepatic mitochondrial dysfunction under oxidative damages induced by organic hydroperoxide, tert-butyl hydroperoxide (tBHP), for estimation of the molecular targets impaired during oxidative stress, and for investigation of the role of Ca(2+) ions in mitochondrial oxidative reactions and of the protective effect of melatonin during mitochondrial peroxidative damage.
  
  
  METHODS
  Mitochondria were isolated by differential centrifugation from the rat liver. The effects of tBHP exposure, EDTA, Ca(2+) ions and melatonin on mitochondrial respiratory activity, mitochondrial enzyme activities and redox status were measured.
  
  
  RESULTS
  The present study provides evidence that tBHP (at low concentrations of 0.02-0.065mM, in EDTA-free medium) induced uncoupling of the oxidation and phosphorylation processes and decreased the efficiency of the phosphorylation reaction. This effect depended on the respiratory substrate used. The presence of EDTA prevented oxidative impairment of mitochondrial respiration, but Ca(2+) ions in the medium enhanced oxidant-induced mitochondrial damage considerably. In the presence of 0.5mM EDTA, tBHP (at high concentrations, 0.5-2mM) considerably oxidized mitochondrial reduced glutathione, enhanced accumulation of membrane lipid peroxidation products and mixed protein-glutathione disulfides and led to an inhibition of oxoglutarate dehydrogenase and succinate dehydrogenase.
  
  
  CONCLUSIONS
  Direct oxidative modification of enzymatic complexes of the respiratory chain and mitochondrial matrix, mitochondrial reduced glutathione depletion, protein glutathionylation, membrane lipid peroxidation and Ca(2+) overload are the main events of mitochondrial peroxidative damages. Experiments in vitro demonstrated that melatonin inhibited the mitochondrial peroxidative damage, preventing redox-balance changes and succinate dehydrogenase inactivation.
authors: Department of Biochemistry, Yanka Kupala Grodno State University, Blvd. Len. Kom., 50, 230017 Grodno, Belarus. zavodnik_il@mail.ru
authors: Ilya B
authors: IB
authors: Zavodnik
authors: Iosif K
authors: IK
authors: Dremza
authors: Vitali T
authors: VT
authors: Cheshchevik
authors: Elena A
authors: EA
authors: Lapshina
authors: Maria
authors: M
authors: Zamaraewa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008550:Melatonin / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D013385:Succinate Dehydrogenase / Q000378:metabolism; D020122:tert-Butylhydroperoxide / Q000494:pharmacology*
chemical_list: D020122:tert-Butylhydroperoxide; D004492:Edetic Acid; D007655:Ketoglutarate Dehydrogenase Complex; D013385:Succinate Dehydrogenase; D008550:Melatonin; D002118:Calcium