Alloxan-induced mitochondrial permeability transition triggered by calcium, thiol oxidation, and matrix ATP.
In addition to their critical function in energy metabolism, mitochondria contain a permeability transition pore, which is regulated by adenine nucleotides. We investigated conditions required for ATP to induce a permeability transition in mammalian mitochondria. Mitochondrial swelling associated with mitochondria permeability transition (MPT) was initiated by adding succinate to a rat liver mitochondrial suspension containing alloxan, a diabetogenic agent. If alloxan was added immediately with or 5 min after adding succinate, MPT was strikingly decreased. MPT induced by alloxan was inhibited by EGTA and several agents causing thiol oxidation, suggesting that alloxan leads to permeability transition through a mechanism dependent on Ca(2+) uptake and sulfhydryl oxidation. Antimycin A and cyanide, inhibitors of electron transfer, carbonyl cyanide m-chlorophenylhydrazone, and oligomycin all inhibited MPT. During incubation with succinate, alloxan depleted ATP in mitochondria after an initial transient increase. However, in a mitochondrial suspension containing EGTA, ATP significantly increased in the presence of alloxan to a level greater than that of the control. These results suggest the involvement of energized transport of Ca(2+) in the MPT initiation. Addition of exogenous ATP, however, did not trigger MPT in the presence of alloxan and had no effect on MPT induced by alloxan. We conclude that alloxan-induced MPT requires mitochondrial energization, oxidation of protein thiols, and matrix ATP to promote energized uptake of Ca(2+).
Sakurai
K
K
Department of Biochemistry, Hokkaido College of Pharmacy, 7-1 Katsuraoka-cho, Otaru, Hokkaido 047-0264, Japan. ks51@hokuyakudai.ac.jp
Katoh
M
M
Fujimoto
Y
Y
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000496:Alloxan / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D007425:Intracellular Membranes / Q000187:drug effects*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism*
D013438:Sulfhydryl Compounds; D000496:Alloxan; D000255:Adenosine Triphosphate; D002118:Calcium