Fig. 2. Kinetics of the mitochondrial proton leak at 25 °C for hypoxic submerged frogs (Rana temporaria). The proton conductance of the mitochondrial inner membrane is assayed by measuring the rate of proton cycling (measured as rate of oxygen consumption) through non-coupled pathways at defined values of the proton-motive force (measured as membrane potential). Stepwise changes in respiration rate and membrane potential were achieved by adding increasing amounts of malonate. The control, 1-month-submerged and 4-month-submerged groups of frogs are represented by black, grey and white circles, respectively. Values are means ± S.E.M.; N=5 for control and 1-month-submerged frogs, N=4 for 4-month-submerged frogs. From St-Pierre et al. (2000a).