INFLUENCE OF METABOLIC-INHIBITORS ON MITOCHONDRIAL PERMEABILITY TRANSITION AND GLUTATHIONE STATUS

Treatment of isolated mitochondria with Ca2+ and inorganic phosphate ( P-i) induces an inner membrane permeability that appears to be mediate d through a cyclosporin A (CsA)-inhibitable Ca2+-dependent pore. Isola ted mitochondria during inner membrane permeability undergo rapid effl ux of matrix solutes such as glutathione as GSH and Ca2+, loss of coup led functions, and large amplitude swelling. Permeability transition w ithout large amplitude swelling, a parameter often used to assess inne r membrane permeability, has been observed. The addition of either oli gomycin, antimycin, or sulfide to incubation buffer containing Ca2+ an d P-i abolished large amplitude swelling of mitochondria. The GSH stat us during a Ca2+- and P-i-dependent mechanism of mitochondrial GSH rel ease in isolated mitochondria was influenced significantly by metaboli c inhibitors of the respiratory chain but did not prevent inner membra ne permeability as demonstrated by the release of mitochondrial GSH an d Ca2+. The release of GSH was inhibited by the addition of CsA, a pot ent inhibitor of permeability transition. Under these conditions we di d not find GSSG; however, rapid oxidation of pyridine nucleotides and depletion of ATP and ADP with conversion to AMP occurred. The addition of CsA, prevented the oxidation of pyridine nucleotides and depletion of ATP and ADP. Since NADH and NADPH were extensively oxidized, prote ction against oxidative stress is reflected in maintenance of GSH and not observable lipid peroxidation. Evidence from transmission electron microscopy analysis, combined with the GSH release data, indicate tha t permeability transition can be observed in the absence of large ampl itude swelling.