Table 5.

Advantages and disadvantages of respirometry measurements in fresh and frozen tissue samples. Abbreviations: ATP: Adenosine triphosphate; TCA: Tricarboxylic acid cycle.

	Fresh	Frozen
Advantages	Greater physiological context Coupled mitochondria that synthesize ATP Intact mitochondria that maintain morphology with some techniques Metabolic pathways and transporters can be investigated Respiration can be measured in intact and permeabilized cells and isolated mitochondria	Integrated oxygen consumption measurement Maximal respiratory capacity often correlates with disease phenotypes Minimal sample requirement and processing Samples can be collected off-site Samples can be stored and run together in one assay Maximal respiration can be measured in homogenates and normalized to mitochondrial content
Drawbacks	Samples have to be processed and run on the same day Mitochondrial isolation requires sufficient starting material Control and patient samples cannot always be run simultaneously increasing variability	Samples are not coupled and ATP synthesis capacity cannot be assessed Broken mitochondria that do not maintain mito-chondrial morphology or membrane integrity Metabolic pathways cannot be assessed TCA cycle and transporters are not active