Ca(2+)-induced, phospholipase-independent injury during reoxygenation of anoxic mitochondria.
Reoxygenation of rat-liver mitochondria after anoxic incubation induced release of matrix proteins. As assessed by release of a matrix enzyme, it was proportional to the rate of H2O2 production. The release was not observed with low concentrations of extramitochondrial free Ca2+, indicating a Ca(2+)-dependent pathway. Phospholipase A2 was not involved in the reoxygenation injury, because non-esterified fatty acids did not increase on reoxygenation even when re-acylation was inhibited and because inhibitors of phospholipase A2 had little effect on enzyme release. Cyclosporin A, ATP, ADP and inhibitors of pyridine nucleotide oxidation had a protective effect, strongly suggesting involvement of so-called Ca(2+)-dependent permeability transition. Ca2+ was also released from reoxygenated mitochondria and inhibition of reuptake of released Ca2+ attenuated the enzyme release. Similar releases of aspartate aminotransferase and Ca2+ were observed with mitochondria in an oxygen radical-generating system, hypoxanthine and xanthine oxidase. In this system, lecithin-cardiolipin liposomes also released entrapped Ca2+ without disruption of the membrane. From these results, we conclude that during reoxygenation, Ca2+ release and subsequent reuptake induced permeability transition of mitochondria, resulting in reoxygenation injury.
Inoue
T
T
Department of Physiological Chemistry, Osaka University Medical School, Japan.
Yoshida
Y
Y
Nishimura
M
M
Kurosawa
K
K
Tagawa
K
K
D000818:Animals; D001219:Aspartate Aminotransferases / Q000032:analysis; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D006706:Homeostasis; D007511:Ischemia / Q000378:metabolism; D008099:Liver / Q000098:blood supply; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D010084:Oxidation-Reduction; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D017207:Rats, Sprague-Dawley
D001219:Aspartate Aminotransferases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium