Research Paper Volume 5, Issue 11 pp 850—864

Figure 1. OCR and ECAR profiles.

Description of the oxygen consumption rate (OCR) (A) and extracellular acidification rate (ECAR) (B) parameters determined in this manuscript; for this illustration, data curves generated from a randomly selected participant in this study were used. Basal OCR and ECAR were measured (simultaneously), followed by measurements taken after sequential addition of oligomycin (1 μM), FCCP (0.3 μM) and antimycin A (2 μM). The fourth rate measurement after the beginning of the run and after each drug was added was used for the OCR and ECAR measurements, to allow for equilibration (rates 4, 8, 12, and 16 as shown). The first drug added was oligomycin. This drug inhibits ATP synthesis by blocking the proton channel of ATP synthase (Complex V). This results in a decrease in OCR to the extent to which the cells are using mitochondria to generate ATP. The remaining OCR is due to proton leak across the mitochondrial membrane and non-mitochondrial sources such as various desaturase and detoxification enzymes. There will be a concomitant increase in ECAR as the cells revert to glycolysis to meet their energy demands (this parameter is termed glycolytic reserve). The next drug added was FCCP, which is an uncoupling agent that disrupts ATP synthesis by transporting hydrogen ions across the mitochondrial membrane instead of the proton channel of ATP synthase. This leads to a rapid consumption of oxygen without the generation of ATP. ECAR may increase slightly beyond the existing ECAR as the cells continue to attempt to maintain their energy balance by using glycolysis to generate ATP. The final drug added was antimycin A, a complex III inhibitor. This causes the flow of electrons through the electron transport chain to cease. Therefore, consumption of oxygen is drastically reduced. Again, the ECAR may also increase slightly if necessary to maintain cellular energy balance.