FIGURE 2.

A and B, the superoxide signal was unaltered in mitochondria from control and denervated muscle by EPR. A shows the EPR traces of DIPPMPO-measured superoxide release from skeletal muscle mitochondria in the absence (State 1) and presence of respiratory substrate, glutamate/malate (G/M) (5 mm). Each trace shows the average of four independent animals, with 10 scans performed for each. The quantified data are presented (n = 4–5, mean ± S.E.) in Fig. 2B (control (CTL), white bar; denervated (DN), black bars). C, aconitase activity does not change with denervation. Muscle homogenate (0.5 mg of protein/ml) was incubated with buffers (with or without isocitrate dehydrogenase), and aconitase activity was measured at 355-nm excitation and 460-nm emission. The difference in fluorescence reading in the presence/absence of isocitrate dehydrogenase was taken as a measure of aconitase activity. The results are expressed as the means ± S.E. of 4–5 experiments (control, white bar; denervated, black bar). D, no difference in superoxide release in mitochondria from control and denervated muscles by the MCLA probe. Mitochondria isolated from control and denervated muscles were incubated in the presence of MCLA, and fluorescence was measured at ∼465 nm. The MCLA signal was undetectable in mitochondria isolated from control and denervated muscle in the absence of respiratory substrates (State 1). No difference in the MCLA signal was detected in the presence of respiratory substrate, glutamate/malate. The results are expressed as the means ± S.E. of nine experiments (control, white bars; denervated, black bars).