OPENING OF THE MITOCHONDRIAL PERMEABILITY TRANSITION PORE BY UNCOUPLING OR INORGANIC-PHOSPHATE IN THE PRESENCE OF CA2-GENERATED REACTIVE OXYGEN SPECIES( IS DEPENDENT ON MITOCHONDRIAL)

In this study, we show that mitochondrial membrane permeability transi tion in Ca2+-loaded mitochondria treated with carbonyl cyanide p-(trif luoromethoxy)phenylhydrazone (FCCP) or inorganic phosphate (P-i) is pr eceded by enhanced production of H2O2. This production is inhibited ei ther by ethylene glycol-bis(b-aminoethyl ether)N,N,N',N'-tetraacetic a cid (EGTA) or Mg2+, but not by cyclosporin A, Permeability transition is prevented either by EGTA, catalase or dithiothreitol, suggesting th e involvement of Ca2+, H2O2 and oxidation of membrane protein thiols i n this mechanism, When mitochondria are incubated under anaerobiosis, no permeabilization or H2O2 production occurs, Based on these results we conclude that mitochondrial permeability transition induced by P-i or FCCP-uncoupling is dependent on mitochondrial-generated reactive ox ygen species.