Determination of the mitochondrial activity of glutathione peroxidase/reductase system and ability to metabolize organic peroxide. (a) Isolated mouse and marsupial liver mitochondria (LM; 1 mg/mL) were added to standard reaction medium containing 500 μM GSH and 100 μM NADPH. Triton X-100 (0.1%) was also presented to lyse the mitochondria. The reaction started after the addition of 0.5 mM tert-butyl hydroperoxide (t-BOOH). Lines are representative of three independent experiments. (b) LM (0.5 mg/mL) were incubated in standard medium containing 5 mM succinate, 1 μM rotenone, and 300 μM EGTA. Where indicated by the arrow, 15 μM t-BOOH was added. Traces are representative of 4 independent experiments.