- First, mitochondrial respiration will be measured by high resolution respirometry (Oxygraph, Oroboros Instruments, Innsbruck, Austria) using a stepwise protocol to evaluate various components of the electron transport system. Protein content of the mitochondrial suspension will be measured using a colorimetric assay (Pierce 660-nm Protein Assay). Oxygen flux rates will be expressed per tissue-wet weight and per milligram of mitochondrial protein.