Cytochrome c potentiates fatty acid-induced cyclosporin A-sensitive permeability transition in liver mitochondria.

Addition of 0.5-5 microM cytochrome c and 30 microM lauric acid to rat liver mitochondria stimulated the respiration rate. Stimulation of respiration by cytochrome c was prevented by cyclosporin A and was not observed in the absence of lauric acid. High amplitude swelling of mitochondria in the presence of lauric acid was also potentiated by cytochrome c; this effect was prevented by cyclosporin A or by EGTA. Polylysine (0.35 microM) induced cyclosporin A-insensitive high amplitude swelling of mitochondria. Polylysine-induced swelling was stimulated by lauric acid and cytochrome c; the effect was prevented by cyclosporin A. Incubation of mitochondria with 30 microM lauric acid resulted in an increase in cytochrome c concentration in the incubation medium. Added cytochrome c is supposed to potentiate the laurate-induced cyclosporin A-sensitive permeability transition in cytochrome c-depleted mitochondria.