The role of phospholipase A2 in lipid peroxidation-induced fall of membrane potential of rat liver mitochondria

AbstractCumene hydroperoxide (230 μM)-induced fall of the membrane potential takes place only in Ca2+ -loaded mitochondria. Inhibitor of phospholipase A2, P-bromphenacyl bromide prevents uncoupling of mitochondria, having no effect on the accumulation of lipid peroxidation products

Inhibitors of the ATP/ADP antiporter suppress stimulation of mitochondrial respiration and H+ permeability by palmitate and anionic detergents

AbstractThe action of ATP/ADP-antiporter inhibitors upon the uncoupling effect of palmitate, detergents and ‘classical’ uncouplers has been studied. The uncoupling effect was estimated by stimulation of succinate oxidation and of H+ permeability of rat liver mitochondria in the presence of oligomycin. It is shown that carboxyatractylate (CAtr) and pyridoxal 5-phosphate (PLP) suppress the uncoupling induced by palmitate and the anionic detergents SDS and cholate, but do not affect that induced by the cationic detergents CTAB, by the non-ionic detergent Triton X-100, as well as by the ‘classical’ uncouplers FCCP and DNP. The results are discussed in terms of a concept assuming that the ATP/ADP-antiporter facilitates the electrophoretic export of hydrophobic anions from mitochondria

Reversible inhibition of electron transfer in the ubiquinol Cytochrome c reductase segment of the mitochondrial respiratory chain in hibernating ground squirrels

AbstractElectron transfer through the ubiquinol:cytochrome c1-segment of liver mitochondria isolated from hibernating ground squirrels Citellus undulatus is repressed by 70–80% as compared to mitochondria from the active animals. The inhibition site is likely to be localized between ubiquinone and the cytochrome bc1, complex. Partial release of the inhibition can be observed upon swelling of the isolated mitochondria in a hypoosmotie medium, the effect being prevented by phospholipase A2 inhibitors. Possible role of phospholipase A2 in regulation of ubiquinol oxidation by complex bc1, is discussed

Cyclosporin A suppression of uncoupling in liver mitochondria of ground squirrel during arousal from hibernation

AbstractEnergy coupling parameters were studied in liver mitochondria of ground squirrel during arousal from hibernation. It was found that such mitochondria become uncoupled during incubation with phosphate in a salt medium. The uncoupling was revealed by respiration rate increase and membrane potential decrease in the presence of oligomycin. Both effects were reversed by addition of cyclosporin A. Under the same in vitro conditions, mitochondria from aroused (active) animals showed no uncoupling but could be uncoupled by addition of palmitate in the cyclosporin A-sensitive fashion. It is proposed that formation of cyclosporin A-sensitive pores can be involved in urgent heat production in arousing hibernators