Ca2+ ion accumulation precedes formation of O2-* in isolated brain mitochondria.
The relationship between mitochondrial Ca2+ accumulation and reactive oxygen species formation is studied by means of fast kinetics with fluorescence detection. Succinate or elevated [Na+] and [Ca2+] provided alternative conditions for induction of reactive oxygen species in isolated rat cerebrocortical mitochondria. Depending on Na+/Ca2+ exchanger and superoxide dismutase activities, formation of reactive oxygen species in mitochondria exposed to elevated [Na+] and [Ca2+] levels was characterized by t(1/2) = 12.3+/-2.9 ms. Production of reactive oxygen species by xanthine oxidase followed a similar time course. Both the processes were blocked by para-benzoquinone, indicating the primary formation of O2-*. Substantial increase in mitochondrial O2-*. was observed at [Ca2+] > or = 2.5 microM. Mitochondrial Ca2+ accumulation obeyed similar [Ca2+] dependence but shorter t(1/2) (2.5+/-0.3 ms), providing kinetic evidence for Ca2+ accumulation-dependent primary formation of O2-* in brain mitochondria.
Szárics
Eva
E
Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Centre, Hungarian Academy of Sciences, Budapest, Hungary.
Kovács
Richárd
R
Hajós
Ferenc
F
Kardos
Julianna
J
D000818:Animals; D001921:Brain / Q000648:ultrastructure*; D002118:Calcium / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
D017382:Reactive Oxygen Species; D019831:Sodium-Calcium Exchanger; D013482:Superoxide Dismutase; D010100:Oxygen; D002118:Calcium