scholarly journals Free-radical metabolism of carbon tetrachloride in rat liver mitochondria. A study of the mechanism of activation

1987 ◽  
Vol 246 (2) ◽  
pp. 313-317 ◽  
Author(s):  
A Tomasi ◽  
E Albano ◽  
S Banni ◽  
B Botti ◽  
F Corongiu ◽  
...  
Keyword(s):  
Free Radical ◽  
Carbon Tetrachloride ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Radical Species ◽  
Hypoxic Conditions ◽  
Free Radical Species ◽  
Transport Chain

Alterations in liver mitochondria as consequence of rat poisoning with carbon tetrachloride (CCl4) have been reported over many years, but the mechanisms responsible for causing such damage are still largely unknown. Isolated rat liver mitochondria incubated under hypoxic conditions with succinate and ADP were found able to activate CCl4 to a free-radical species identified as trichloromethyl free radical (CCl3) by e.s.r. spectroscopy coupled with the spin-trapping technique. The incubation of mitochondria in air decreased free-radical production, indicating that a reductive reaction was involved in the activation of CCl4. However, in contrast with liver microsomes (microsomal fractions), mitochondria did not require the presence of NADPH, and the process was not significantly influenced by inhibitors of cytochrome P-450. The addition of inhibitors of the respiratory chain such as antimycin A and KCN decreased free-radical formation by only 30%, whereas rotenone displayed a greater effect (approx. 84% inhibition), but only when preincubated for 15 min with mitochondria not supplemented with succinate. These findings suggest that the mitochondrial electron-transport chain is responsible for the activation of CCl4. A conjugated-diene band was observed in the lipids extracted from mitochondria incubated with CCl4 under anaerobic conditions, indicating that stimulation of lipid peroxidation was occurring as a result of the formation of free-radical species.

Toxicity of bile acids on the electron transport chain of isolated rat liver mitochondria

Hepatology ◽  
1994 ◽  
Vol 19 (2) ◽  
pp. 471-479 ◽  
Author(s):  
Stephan Krähenbühl ◽  
Christine Talos ◽  
Sven Fischer ◽  
Jürg Reichen
Keyword(s):  
Electron Transport ◽  
Bile Acids ◽  
Rat Liver ◽  
Electron Transport Chain ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Transport Chain ◽  
Isolated Rat

scholarly journals Spin-trapping studies on the free-radical products formed by metabolic activation of carbon tetrachloride in rat liver microsomal fractions isolated hepatocytes and in vivo in the rat

1982 ◽  
Vol 204 (2) ◽  
pp. 593-603 ◽  
Author(s):  
E Albano ◽  
K A K Lott ◽  
T F Slater ◽  
A Stier ◽  
M C R Symons ◽  
...  
Keyword(s):  
Free Radical ◽  
Carbon Tetrachloride ◽  
Spin Trap ◽  
Peroxy Radical ◽  
Metabolic Activation ◽  
Spin Trapping ◽  
Metabolic Inhibitors ◽  
Radical Species ◽  
Free Radical Species ◽  
Trichloromethyl Radical

1. The metabolic activation of carbon tetrachloride to free-radical intermediates is an important step in the sequence of disturbances leading to the acute liver injury produced by this toxic agent. Electron-spin-resonance (e.s.r.) spin-trapping techniques were used to characterize the free-radical species involved. 2. Spin trapping was applied to the activation of carbon tetrachloride by liver microsomal fractions in the presence of NADPH, and by isolated intact rat hepatocytes. The results obtained with the spin trap N-benzylidene-2-methylpropylamine N-oxide (‘phenyl t-butyl nitrone’) (PBN) and [13C]carbon tetrachloride provide unequivocal evidence for the formation and trapping of the trichloromethyl free radical in these systems. 3. With the spin trap 2-methyl-2-nitrosopropane, however, the major free-radical species trapped are unsaturated lipid radicals produced by the initiating reaction of lipid peroxidation. 4. Although pulse radiolysis and other evidence support the very rapid formation of the trichloromethyl peroxy radical from the trichloromethyl radical and oxygen, no clear evidence for the trapping of the peroxy radical was obtainable. 5. The effects of a number of free-radical scavengers and metabolic inhibitors on the formation of the PBN-trichloromethyl radical adduct were studied, as were the influences of changing the concentration of PBN and incubation time. 6. High concentrations of the spin traps used were found to have significant effects on cytochrome P-450-mediated reactions; this requires caution in interpreting results of experiments done in the presence of PBN at concentrations greater than 50 mM.

scholarly journals THE RATIO OF UBIQUINON REDOX FORMS IN THE RAT LIVER MITOCHONDRIA UNDER CONDITIONS OF DIFFERENT NUTRIENT SUPPLY

2020 ◽  
Vol 66 (6) ◽  
pp. 82-87
Author(s):  
O.M. Voloshchuk ◽  
◽  
G. P. Kopylchuk ◽  
М.S. Ursatyу ◽  
◽  
...  
Keyword(s):  
Free Radical ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Oxidative Modification ◽  
Mitochondrial Proteins ◽  
Rat Liver Mitochondria ◽  
Carbonyl Derivatives ◽  
High Sucrose Diet ◽  
Redox Forms ◽  
High Sucrose

The relationship between the quantitative ratio of redox forms of ubiquinone and the degree of free radical damage to mitochondrial proteins in rat liver against the background of nutritional imbalance was investigated. The animals were divided into the following experimental groups: I – animals receiving full-value semi-synthetic ration (control group); II – animals receiving high-sucrose diet; III – animals receiving low-protein high-sucrose diet. The content of total and oxidized ubiquinone was determined spectrophotometrically at 275 nm, the content of reduced ubiquinone was determined by the difference between the content of total and oxidized ubiquinone. The intensity of the oxidative modification of proteins was assessed by the accumulation of carbonyl derivatives in the reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH), the content of free SH-groups was assessed by using the Elman reagent. It was found that the most pronounced decrease in the content of total ubiquinone (almost twice) and the redistribution of its redox forms (reduction of the content of reduced ubiquinone by 7.2 times against the background of an increase in the level of oxidized ubiquinone by 2 times) in rat liver mitochondria is observed in animals that received a diet high in sucrose against the background of alimentary protein deprivation. In addition, the animals of this group showed the most pronounced free radical oxidation of mitochondrial proteins, as evidenced by a 3.5-fold increase in the content of carbonyl derivatives and a 2.6-fold decrease in the content of free protein SH- groups. It was shown that nutritional protein deficiency is a critical factor affecting the intensity of free radical processes in mitochondria. The established changes in the ratio of the redox forms of ubiquinone and the degree of oxidative modification of mitochondrial proteins in rat liver could be considered as prerequisites for deepening the energy imbalance and violation of the functional activity of mitochondria under conditions of nutritional imbalance.

scholarly journals Contamination by rough microsomes of rat liver mitochondria during poisoning by carbon tetrachloride

Micron (1969) ◽  
1979 ◽  
Vol 10 (3) ◽  
pp. 167-168
Author(s):  
Michael J. Brabec ◽  
Roberta K. Brabec ◽  
Robert H. Gray
Keyword(s):  
Carbon Tetrachloride ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals The action of paraquat and diquat on the respiration of liver cell fractions

1968 ◽  
Vol 109 (5) ◽  
pp. 757-761 ◽  
Author(s):  
J C Gage
Keyword(s):  
Oxygen Uptake ◽  
Nadph Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Nadh Oxidase ◽  
Liver Microsomes ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Rat Liver Microsomes ◽  
Nadph Oxidase Activity

1. Paraquat and diquat produce only a slight increase in the oxygen uptake of rat liver mitochondria, and it is likely that they do not penetrate the mitochondrial membrane. 2. In mitochondrial fragments inhibited by antimycin A or by Amytal, both substances stimulate oxygen uptake with NADH or β-hydroxybutyrate as substrate but not with succinate. The NADH dehydrogenase of the respiratory chain appears to be involved, at a site only partially inhibited by Amytal. 3. An NADPH oxidase activity is stimulated in rat liver microsomes by diquat, and to a smaller extent by paraquat; diquat also causes an NADH oxidase activity to develop. The effect is not inhibited by carbon monoxide or p-chloromercuribenzoate, and it is probable that a flavoprotein is involved by a mechanism not requiring thiol groups. 4. One molecule of oxygen can oxidize two molecules of NADPH in the stimulated microsomal system, the hydrogen peroxide produced being broken down by a catalase activity in the microsomes. 5. Diquat can stimulate NADH oxidase and NADPH oxidase activity in the postmicrosomal soluble fraction; the enzyme involved may be DT-diaphorase. 6. The mechanism of these reactions and their significance in relation to the toxicity of the dipyridilium compounds are discussed.

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