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Chromium ions inactivate electron transport and enhance superoxide generation in vivo in pea ( Pisum sativum L. cv. Azad) root mitochondria
Author(s) -
Dixit V.,
Pandey V.,
Shyam R.
Publication year - 2002
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2002.00843.x
Subject(s) - submitochondrial particle , superoxide , cytochrome c , chemistry , biochemistry , electron transport chain , nadh dehydrogenase , lipid peroxidation , hexavalent chromium , superoxide dismutase , radical , oxidoreductase , succinate dehydrogenase , mitochondrion , chromium , antioxidant , enzyme , organic chemistry , protein subunit , gene
The effect in vivo of hexavalent chromium (Cr 6+ ) on the respiratory electron transport activity and production of superoxide (O 2 – ) radicals, was studied in submitochondrial particles (SMPs) prepared from mitochondria isolated from roots of 15‐day‐old pea ( Pisum sativum L. cv. Azad) plants exposed to environmentally relevant (20 µ m ) and acute (200 µ m ) concentrations of chromium for 7 d. A concentration ‐dependent inactivation of electron transport activity from both NADH to O 2 (NADH oxidase) and succinate to O 2 (succinate oxidase) was observed. The electron transport activity was more sensitive to Cr 6+ with NADH as the substrate than with succinate as the substrate. Although NADH dehydrogenase and succinate dehydrogenase were less affected, NADH: cytochrome c oxidoreductase and succinate: cytochrome c oxidoreductase activities were prominently affected by Cr 6+ . Cytochrome oxidase was the most susceptible complex of mitochondrial membranes to Cr 6+ , exhibiting maximal inactivation of activity both at 20 and 200 µ m chromium concentrations. Cr 6+ increased the generation of O 2 – radicals. This effect was more evident at 200 than at 20 µ m . A significant increase in lipid peroxidation of mitochondrial membranes at 200 µ m Cr 6+ was the physiological impact of the metal‐induced enhanced generation of O 2 – radicals. An increase in superoxide dismutase (SOD) activity at 20 µ m Cr 6+ towards enhanced production of O 2 – radicals appeared to be a defence response in pea root mitochondria that, however, could not be sustained at 200 µ m Cr 6+ . The results obtained concerning inactivation of mitochondrial electron transport and subsequent enhancement in the generation of O 2 – radicals suggest that root mitochondria are an important target of Cr 6+ ‐induced oxidative stress in pea.