Effect of cyclosporin A on energy coupling in pea stem mitochondria is studied. It is found that incubation of mitochondria with 100 nM FCCP and/or CAtr, oligomycin, CaCl2, palmitate and ADP results, after some lag phase, in a collapse of Δψ generated by Succinate oxidation in the presence of rotenone. Cyclosporin A (0.2-0.8 nmol/mg mitochondrial protein) markedly increases the lag phase. The cyclosporin A effect requires dithioerythritol to be added to the isolation medium. Metabisulphite fails to substitute for dithioerythritol. The relationships between these effects and cyclosporin A-sensitive mitochondrial permeability transition in animal mitochondria are discussed.
