(A–B) Relative respiration rate in permeabilized gastrocnemius muscle fibers from transgenic mice (p43) and wild-type animals (WT) at 2 and 6 months of age (n = 5 in each group). Respiration parameters were recorded at 25°C using an Oroboros oxygraph. Resting respiration (V0) was initiated in the presence of complex I (5 mM malate and 5 mM pyruvate) or complex II substrates (10 mM succinate and 2.5 µM rotenone), and maximal ADP-stimulated respiration was measured with one addition of saturating ADP concentration (1 mM)(Vmax). MP: malate and pyruvate; SR: succinate and rotenone. *p<0.05. Control values at each stage are considered as 100%, and p43 value are expressed in percent of the corresponding control value.