Effect of micromolar Ca2+ concentration on membrane potential of mouse and marsupial liver mitochondria. (a) Determination of membrane potential in isolated mouse and marsupial liver mitochondria. Liver mitochondria (0.5 mg/mL) were added to the incubation medium containing 200 μM EGTA, NADH-linked respiratory substrates (2 mM malate, 1 mM pyruvate, 1 mM α-ketoglutarate and 1 mM glutamate), and 5 μM safranine. The arrows indicate where 150 μM ADP, 40 ng/mL valinomycin (Val), and KCl (each addition: 350 μM) were added to the experiments. (b) Effect of Ca2+ on mitochondrial membrane potential. Ca2+ (40 μM) was added to the experiments which was indicated by the arrow. Cyclosporin A (CsA; 1 μM), a mitochondrial permeability transition inhibitor, was present in the incubation medium where indicated. Traces are representative of 3 independent experiments.