(D) Substrate-dependent oxygen consumption rates in isolated heartmitochondria. Complex I substrates (pyruvate, malate, glutamate); complex II substrate (succinate). State 3 - ADP stimulated oxygen consumption rate; State 4 - respiration rate after addition of oligomycin; Uncoupled - oxygen consumption rate in the presence of FCCP. Bars present mean levels ± SD. Student's t-test was used to determine the level of statistical difference (n=7). 