Fig. 5. Mitochondrial oxygen consumption (% of oxygen consumption rate at air saturation) as a function of oxygen concentration (µmoll^–1). State 3 respiration was recorded with 8 mmoll^–1 malate added as a substrate in the presence of 0.5 mmoll^–1 salicylhydroxamic acid (SHAM) (black dots) and with 50 µmoll^–1 sulfide added as a substrate in the presence of 1 mmoll^–1 DHA (open squares) or in the presence of 2.5 mmoll^–1 GSH + 2.5 mmoll^–1 ascorbate (gray circles). Mitochondria were allowed to completely consume the oxygen contained in the respiration medium, thus providing respiration rates at variable oxygen concentrations.