Fatty acid-induced uncoupling of oxidative phosphorylation is partly due to opening of the mitochondrial permeability transition pore.

Addition of myristate at low concentration (30-60 nmol/mg protein) to energized rat liver mitochondria resulted in dissipation of the electric membrane potential which, in Ca2+-free media, could be partly reversed by carboxyatractyloside but not by cyclosporin A. In contrast, in mitochondria preloaded with Ca2+ this energy-dissipating effect of fatty acid was partly prevented or reversed by cyclosporin A or ADP. In sucrose media, myristate, but not the protonophore carbonyl cyanide m-chlorophenylhydrazone, induced swelling of Ca2+-loaded mitochondria which was inhibited by cyclosporin A and ADP. We conclude that long-chain fatty acids may induce opening of the mitochondrial permeability transition pore not only because of their protonophoric effect mediated by mitochondrial anion carriers [Skulachev, V.P., FEBS Lett. 294 (1991) 158-162; Wieckowski, M.R. and Wojtczak, L., Biochem. Biophys. Res. Commun. (1997) 232, 414-417] but also by a direct interaction with the pore assembly.