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Biomedical subjects

E Cadenas

Publications and source records attributed to E Cadenas.

130 records · Page 8Linked to original sources
PubMed1976

Role of ubiquinone in the mitochondrial generation of hydrogen peroxide.

Antimycin-inhibited bovine heart submitochondrial particles generate O2- and H2O2 with succinate as electron donor. H2O2 generation involves the action of the mitochondrial superoxide dismutase, in accordance with the McCord & Fridovich [(1969) j. biol. Chem. 244, 6049-6055] reaction mechanism. Removal of ubiquinone by acetone treatment decreases the ability of mitochondrial preparations to generate O2- and H2O2, whereas supplementation of the depleted membranes with ubiquinone enhances the peroxide-generating activity in the reconstituted membranes. Addition of superoxide dismutase to ubiquinone-reconstituted membranes is essential in order to obtain maximal rates of H2O2 generation since the acetone treatment of the membranes apparently inactivates (or removes) the mitochondrial superoxide dismutase. Parallel measurements of H2O2 production, succinate dehydrogenase and succinate-cytochrome c reductase activities show that peroxide generation by ubiquinone-supplemented membranes is a monotonous function of the reducible ubiquinone content, whereas the other two measured activities reach saturation at relatively low concentrations of reducible quinone. Alkaline treatment of submitochondrial particles causes a significant decrease in succinate dehydrogenase activity and succinate-dependent H2O2 production, which contrasts with the increase of peroxide production by the same particles with NADH as electron donor. Solubilized succinate dehydrogenase generates H2O2 at a much lower rate than the parent submitochondrial particles. It is postulated that ubisemiquinone (and ubiquinol) are chiefly responsible for the succinate-dependent peroxide production by the mitochondrial inner membrane.

Acetone↗
PubMedDate not supplied

Cellular redox changes and response to drugs and toxic agents.

Cellular metabolism and, in particular, oxidation-reduction systems are linked to responses to drugs and toxic agents in several ways. Major connections are given by the NADPH/NADP+ system and the GSH/GSSG system. Intracellular reductive pathways generally use NADPH as the electron donor. From a toxicological point of view, NADPH can be considered both as a "detoxicant" and as a "toxicant". In the former case, NADPH supports the glutathione redox cycle by maintaining a negative redox potential of GSH to permit its detoxication functions to occur. NADPH is also the main donor for reducing equivalents in drug oxidations by the cytochrome P-450-dependent monooxygenase system which, with some notable exceptions, serves important purposes in detoxication. The sources of NADPH reducing equivalents depend on the nutritional state: major sources in the fed state are represented by the cytosolic pentose phosphate shunt dehydrogenases, whereas mitochondrial sources linked to isocitrate dehydrogenase provide the bulk of NADPH reducing equivalents in the fasted state. As a "toxicant", NADPH supports redox cycling reactions involving various drugs and other compounds of quinoid structure, aromatic nitro compounds and iron chelates with formation of superoxide anion radicals and subsequent formation of other oxygen derived radical species. This presentation focuses on recent work carried out with isolated hepatocytes and perfused rat liver with respect to "oxidative stress". The noninvasive techniques of measurement of low-level chemiluminescence and of volatile hydrocarbons (ethane, pentane) as well as glutathione release and calcium release have been employed.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Mitochondrial production of hydrogen peroxide regulation by nitric oxide and the role of ubisemiquinone.

Mitochondria are considered the major cellular site for hydrogen peroxide production, a process that is kinetically controlled by the availability of oxygen and nitric oxide to cytochrome oxidase and of ADP to F1-ATPase. The multisite regulation of mitochondrial respiration and energy-transducing pathways support a critical regulatory role of mitochondrion in cell signaling pathways. The cellular steady-state levels of hydrogen peroxide and the role of mitochondria in maintaining these levels are reviewed.

Animals↗