Fast Determination of Mitochondrial Metabolism and Respiratory Complex Activity in Permeabilized and Intact Cells

Assessment of mitochondrial metabolism is multidimensional and time consuming, usually requiring specific training. Respiration, NADH generation, and mitochondrial membrane potential (ΔΨm) are dynamic readouts of the metabolism and bioenergetics of mitochondria. Methodologies available to determine functional parameters in isolated mitochondria and permeabilized cells are sometimes of limited use or inapplicable to studies in live cells. In particular, the sequential assessment of the activity of each complex in the electron transport chain has not been reported in intact cells. Here, we describe a novel approach to sequentially assess electron flow through all respiratory complexes in permeabilized and intact cells by respirometry. We also describe a highly sensitive and fast method to assess ΔΨm and NADH generation in live cells using plate reader assays. Thus, our combined method allows a relatively inexpensive and fast determination of three major readouts of mitochondrial function in a few hours, using equipment that is frequently available in many laboratories worldwide.