EFFECT OF EXTRACELLULAR CA++ OMISSION ON ISOLATED HEPATOCYTES .2. LOSS OF MITOCHONDRIAL-MEMBRANE POTENTIAL AND PROTECTION BY INHIBITORS OF UNIPORT CA++ TRANSDUCTION

  • 1 May 1988
    • journal article
    • research article
    • Vol. 245  (2) , 501-507
Abstract
Incubation of isolated rat hepatocytes in Ca2+-free medium generates an oxidative stress which causes significant cell injury. Ruthenium red and La+++, which block Ca++ uptake through the mitochondrial uniport, totally prevented malondialdehyde formation, glutathione and protein thiol oxidation and vitamin E loss induced by Ca++ omission. Accordingly, these agents also prevented leakage of intracellular K+ and lactate dehydrogenase. Similar protective effects were provided by the Ca++ chelator ethyleneglycol bis(.beta.-aminoethyl ether)-N,N''-tetraacetic acid. The absence of extracellular Ca++ resulted in a marked decline of the mitochondrial transmembrane potential which could be prevented by ruthenium red, ethylene glycol bis(.beta.-aminoethyl ether)-N,N''-tetraacetic acid, the antioxidant vitamin E and the iron chelator, desferrioxamine. In contrast, oxidative stress induced by treatment with the redox active agent paraquat and 1,3-bis(2-chloroethyl)-1-nitrosourea had little effect on mitochondrial transmembrane potential and malondialdehyde formation and lactate dehydrogenase leakage were not affected by ruthenium red or La+++. These results indicate the incubation of rat hepatocytes in the absence of extracellular Ca++ creates an unusual oxidative stress which markedly affects mitochondrial function. The ability of vitamin E and desferrioxiamine to inhibit the loss of mitochondrial transmembrane potential indicates that oxidative damage is involved in producing mitochondrial dysfunction. Furthermore, the potent inhibitory effects of ruthenium red and La+++ suggest that Ca++ movement through the uniport, perhaps indicative of mitochondrial Ca++ cycling, plays a major role in generating this oxidative stress and promoting cell injury.