Table 1.

The effect of H₂O₂ on the activity of citrate synthase, succinate dehydrogenase, and malate dehydrogenase

	Activity (% of control)
	100 μm H2O2		500 μm H2O2
	5 min	10 min	5 min	10 min
Citrate synthase	ND	ND	98.2  ± 1.8	98.3  ± 1.2
Succinate dehydrogenase	88  ± 1.121-a	76  ± 2.91-a	74  ± 4.61-a	70.8  ± 3.71-a
Malate dehydrogenase	101.2  ± 1.8	104  ± 1.8	97.4  ± 2.3	105  ± 4.1

Nerve terminals were incubated with H₂O₂as indicated, then enzyme activities were determined in assay media containing Triton X-100 to permeabilize the plasma membrane as described in Materials and Methods. Results are expressed as percentage activity of the corresponding controls measured without H₂O₂ treatment. The following activities were taken as 100%: (1) citrate synthase, 778 ± 70 nmol · min⁻¹ · mg⁻¹ protein (n = 4); (2) succinate dehydrogenase, 30 ± 0.69 nmol · min⁻¹ · mg⁻¹ protein (n = 4); and (3) malate dehydrogenase, 12 ± 0.26 μmol · min⁻¹ · mg⁻¹ protein (n = 4). Results are the average of four independent determinations ± SEM. ND, Not determined.

^F1-aSignificantly different from the corresponding control.