[Uncoupling action of fatty acids in liver cells]. / Razobshchaiushchee deistvie zhirnykh kislot v kletkakh pecheni.

Oleate (10-60 microM) stimulates oxygen consumption in hepatocytes in the presence of oligomycin. This stimulation of respiration is partially suppressed by 20 microM carboxyatractylate but is insensitive to 0.5 microM cyclosporin A. The results obtained suggest that fatty acids can uncouple oxidative phosphorylation in hepatocytes and that the uncoupling mechanism is the same as that in isolated mitochondria in the presence of EGTA.

Fatty acid-induced Ca(2+)-dependent uncoupling and activation of external pathway of NADH oxidation are coupled to cyclosporin A-sensitive mitochondrial permeability transition.

Permeabilization of inner mitochondrial membrane by palmitic acid in the presence of Ca2+ (cyclosporin A-sensitive stimulation of respiration, decrease of delta psi and high amplitude swelling) is accompanied by activation of the external pathway of NADH oxidation in liver mitochondria. The "pore"-sealing agents (cyclosporin A, Mg2+ with ADP, and L-carnitine with ATP) are equally effective in preventing the induction of external pathway of NADH oxidation by Ca2+ with palmitate. However, activities of these agents are different in respect to recoupling of permeabilized mitochondria. Participation of cyclosporin A-sensitive "pore" in the fatty acid- and Ca(2+)-dependent induction of external pathway of NADH oxidation and in Ca(2+)-dependent uncoupling is discussed.

[Oxidative phosphorylation uncoupling by fatty acids in liver and muscle mitochondria]. / Razobshchenie okislitel'nogo fosforilirovaniia zhirnymi kislotami v mitokhondriiakh pecheni i myshts.

Pathways and mechanisms of oxidative phosphorylation uncoupling by long-chain fatty acids in liver and muscle mitochondria are considered. A conclusion is drawn that there exist at least three different pathways of uncoupling by fatty acids, namely: (i) a Ca(2+)-dependent cyclosporin A-sensitive pathway; (ii) uncoupling which is inhibited by carboxyatractylate or other inhibitors of the ADP/ATP-antiporter, (iii) uncoupling due to the low protonophoric activity of fatty acids.

[The protective effect of cyclosporine A, carnitine, and Mg(2+) with ADP during calcium(2+)-dependent permeabilization of mitochondria by fatty acids and activation of NADH oxidation by an external pathway]. / Zashchitnyi éffekt tsiklosporina A, karnitina i Mg(2+) s ADP pri Ca(2+)-zavisimoi permeabilizatsii mitokhondrii zhirnymi kislotami i aktivatsii okisleniia NADH po vneshnemy puti.

The ability of cyclosporin A, Mg2+ plus ADP and L-carnitine to enhance energy recoupling in liver mitochondria and to inhibit the induction of the external pathway of NADH oxidation during Ca(2+)-dependent oxidative phosphorylation uncoupling by palmitate has been studied. Cyclosporin A, Mg2+ plus ADP and L-carnitine plus ATP prevent with an equal efficiency the induction of the external pathway of NADH oxidation by palmitate and Ca2+ in mitochondria but differ drastically by their ability to increase the coupling in permeabilized mitochondria. The recoupling effect of cyclosporin is manifested after addition of Mg2+ plus ADP. The protective action of Mg2+ plus ADP is prevented by preincubation with carboxyatractylate. Oxidation of NADH via an external pathway results in delta psi generation, however, only in the presence of the recoupling factors. The role of the cyclosporin-sensitive pore in Ca(2+)-dependent damage of mitochondria as well as in the induction of the external pathway of NADH oxidation is discussed.

[Damage to calcium ion-loaded mitochondria by fatty acids and the protective effect of carnitine]. / Povrezhdenie nagruzhennykh ionami kal'tsiia mitokhondrii zhirnymi kislotami i zashchitnoe deistvie karnitina.

The effect of fatty acids and L-carnitine on Ca2+ retention in rat liver mitochondria have been studied. Ca(2+)-retention was estimated as a sum of consecutive Ca2+ additions which leaded to transient stimulation of respiration coupled with influx of Ca2+ L-carnitine increases the Ca(2+)-retention; such an effect requires ATP. The Ca(2+)-retention was increased in the presence of 50 microM ATP or ADP. In all cases carboxyatractylate prevented the increase in Ca(2+)-retention. Palmitate and FCCP added at concentrations producing similar stimulating effect on respiration inhibit Ca(2+)-retention to about the same degree. The effect of palmitate is strongly diminished by L-carnitine. Again, the L-carnitine effect requires ATP. The data obtained suggest that the protonophoric effect of fatty acid plays a crucial role in Ca(2+)-dependent damage of mitochondria.

Uncoupling effect of fatty acids on heart muscle mitochondria and submitochondrial particles.

The effect of ATP/ADP-antiporter inhibitors on palmitate-induced uncoupling was studied in heart muscle mitochondria and inside-out submitochondrial particles. In both systems palmitate is found to decrease the respiration-generated membrane potential. In mitochondria, this effect is specifically abolished by carboxyatractylate (CAtr) a non-penetrating inhibitor of antiporter. In submitochondrial particles, CAtr does not abolish the palmitate-induced potential decrease. At the same time, bongkrekic acid, a penetrating inhibitor of the antiporter, suppresses the palmitate effect on the potential both in mitochondria and particles. Palmitoyl-CoA which is known to inhibit the antiporter in mitochondria as well as in particles decreases the palmitate uncoupling efficiency in both these systems. These data are in agreement with the hypothesis that the ATP/ADP-antiporter is involved in the action of free fatty acids as natural uncouplers of oxidative phosphorylation.