ABSTRACT
Rat intoxication with acetaminophen (APAP) (500-1500 mg/kg body weight intragastrically) caused a considerable dose-dependent decrease in reduced glutathione (GSH) level in both liver cellular cytoplasm and mitochondria (at the dose 1500 mg/kg body weight by 60% and 33%, respectively). The cytoplasmic GSH level decreased more pronounced by comparison with that in mitochondria. At the same time, we did not observe any inactivation of the mitochondrial enzymes: succinate dehydrogenase, alpha-ketoglutarate dehydrogenase, glutathione peroxidase despite of mitochondrial GSH consumption; also we did not observe any decrease in the respiratory activity of liver mitochondria isolated from APAP-intoxicated rats. A tryptophan derivative, melatonin (10 mg/kg body weight), did not prevent intramitochondrial GSH oxidation, but decreased the hepatoxity of APAP, diminishing the activities of AlT and AsT as well as bilirubin level in blood plasma of intoxicated rats. N-acetyl-nitrosotryptophan (a nitric oxide donor) did not exhibit any hepatoprotective effects.
Subject(s)
Acetaminophen/adverse effects , Analgesics, Non-Narcotic/adverse effects , Antioxidants/pharmacology , Chemical and Drug Induced Liver Injury/prevention & control , Melatonin/pharmacology , Tryptophan/pharmacology , Acetaminophen/pharmacokinetics , Analgesics, Non-Narcotic/pharmacology , Animals , Chemical and Drug Induced Liver Injury/metabolism , Glutathione/metabolism , Liver/metabolism , Male , Mitochondria, Liver/metabolism , Oxidoreductases/metabolism , Rats , Rats, WistarABSTRACT
Hypoclorous acid is an effective biological oxidant produced by activated neutrophils. HOCl plays a role of the major inflammation mediator in mammalian tissues. The aim of the present study was to investigate the mechanisms of hypochlorous acid-induced modification of antioxidant enzymes, which defence the cell under oxidative stress, and enzymes of the pentose phosphate pathway, which supply reducing equivalents in the cell. HOCl (100-1000 microM) in vitro inhibited considerably in a dose-dependent manner the activity of the enzymes of the pentose phosphate pathway in the rat liver postmitochondrial fraction. HOCI at a concentration of 100 nmol/mg protein inhibited transketolase activity by 65 +/- 5%, glucose-6-phosphate dehydrogenase--by 50 +/- 5% and 6-phosphogluconate dehydrogenase--by 55 +/- 5%. The activities of glutathione peroxidase and catalase slightly decreased. On the contrary, in the rat heart postmitochondrial fraction HOCl (100-1000 microM) inhibited considerably catalase, increased glutathione peroxidase activity and decreased significantly the activity of the key enzymes of the pentose phosphate pathway. The inhibition of the pentose phosphate pathway enzymes was accompanied by oxidation of intracellular reduced glutathione, oxidative protein modification (protein carbonyl group accumulation, mixed protein-glutathione disulphides and chloramine formation), and membrane lipid peroxidation. The sensitivity of rat heart cell components to oxidative damage by HOCl was higher in comparison with that of the liver.
