FIGURE 4.

The classic pyruvate transport inhibitor CHC preferentially inhibits uncoupled state 3 respiration. A, state 3 respiration rates were measured in control heart mitochondria in the presence of 1.0 mm malate, 0.1 mm pyruvate, and the indicated amounts of CHC (n = 4). B, representative oxygen consumption traces of control mitochondria in the presence of 1.0 mm malate, 0.1 mm pyruvate, and 1.0 μm CHC as indicated are shown. State 3 respiration was induced by either the addition of ADP (top) or the uncoupler FCCP (bottom). C, the magnitude of state 3 inhibition induced by 1.0 μm CHC was quantified in coupled and uncoupled mitochondria (n = 6). D, PDH activity was measured in control and CHC-treated mitochondria basally and following stimulation of maximal respiration with either ADP or FCCP. PDH activity was measured as described under “Experimental Procedures” (n = 3–5). *, p < 0.05, unpaired Student's t test. Error bars are the standard deviation.