A and B, representative traces of respiration (upper traces) and change in membrane potential (ΔΨ; lower traces) obtained with and without 200 μm ADP or 60 μm 2,4-dinitrophenol (2,4-DNP). Mitochondria were incubated in KCl- or LiCl-based media supplemented with 3 mm succinate plus 3 mm glutamate. These experiments were performed in the absence of oligomycin. C, summary plot of the respiratory rates, including measurements in mannitol–sucrose (MS)-based medium. V2 is the rate of respiration prior to addition of ADP, V3 is the respiratory rate in the presence of ADP, V4 is the respiratory rate after all ADP was depleted, VDNP is the respiratory rate in the presence of 2,4-DNP. RCI, respiratory control index, the ratio of the respiratory rate with 200 μm ADP to the respiratory rate after all added ADP has been phosphorylated, without addition of oligomicin. Data are means ±s.e.m., n = 3.