Table 1 Advantages and disadvantages of working with isolated mitochondria and intact cells
Isolated mitochondriaIntact cells
Relatively simple and well understood. Better for studies of mechanism. No interference from cytosolic factorsLack cellular contextUndisturbed cellular environment; greater physiological relevance. Interactions with the rest of the cell are preservedMore complex, more scope for errors of interpretation. Lack organismal context
Easy to isolate from many adult tissues of wild-type or genetically modified animalsSubject to damage and selection during isolation. Isolation from small or tough tissues can be problematicNo artefacts due to mitochondrial isolation. Cell lines are amenable to genetic manipulation and plate-based assaysCan be hard or impossible to isolate viable primary cells from adult tissues of transgenic animals
Reagents and substrates can be added directly; the experimenter has control over conditionsThe experimenter has to choose appropriate experimental conditionsThe cell sets the mitochondrial environmentMany reagents and substrates are cell-impermeant, restricting experimental options. The experimenter chooses extracellular substrates, hormones and conditions
Methods are generally very well establishedExisting methods often need large amounts of sample; mitochondria from different cell types may be unavoidably aggregatedPlate-based assays allow measurements on tiny amounts of the sample or single cellsMany methods are not sufficiently specific or quantitative
Easy and usually meaningful to normalize to protein or cytochrome contentEffects due to mitochondrial proliferation, localization etc. lost during isolationEffects due to mitochondrial proliferation and localization retainedThe meaning of results changes with normalization (cell number, cell mass, DNA, cytochrome a etc.)