Description
Intact cells (ce) are characterized by an intact cell membrane. Cell viability should be >95% for various experimental investigations, including cell respirometry. In contrast, the cell membrane of intact cells can be permeabilized selectively by mild detergents (digitonin), to obtain the mt-preparation of permeabilized cells used for cell ergometry.
Abbreviation: ce
Reference: MiPNet08.09 CellRespiration
MitoPedia concepts:
Respiratory state
MitoPedia methods:
Respirometry
HRR and intact cells
- For details, see
- Gnaiger 2014 MitoPathways
- Pesta D, Gnaiger E (2012) High-resolution respirometry. OXPHOS protocols for human cells and permeabilized fibres from small biopisies of human muscle. Methods Mol Biol 810:25-58. - »Bioblast link«.
- Cell ergometry
- O2k-Publications: Intact cells
- For details, see
Respiration medium
- The choice of respiratory medium depends on the scientific question and the applied protocol. The advantage of cell culture media is the availability of substrates (e.g. glucose, glutamine), appropriate ionic composition for maintaining the cell membrane potential and intact signalling (particularly high [Ca2+]). Contidions during respiratory measurement can then be maintained close to cell culture conditions.
- Respiration of intact cells may be measured in mitochondrial respiration medium (e.g. MiR06) followed by permeabilization of the cell membrane by digitonin and applying complex SUIT (substrate-uncoupler-inhibitor titration) protocols. Measuring respiration of permeabilized cells, allowing direct access to the mitochondria, is not possible in cell culture media. These media contain high Ca2+ concentrations, important for cell physiology, but damaging for mitochondria, which swell and disrupt.
Respiratory states
- ROUTINE and LEAK respiration, ETS capacity and ROX can be determined in intact cells (see Gnaiger 2014 MitoPathways). These respiratory coupling states can be evaluated in the absence of external substrates on the basis of internal substrate stores (endogenous respiration).
Adherent cells
- The lab of Gregory Brewer developed techniques for high-resolution respirometry with the OROBOROS-O2k of neuronal cells attached to a substrate:
- Jones TT, Brewer GJ (2009) Critical age-related loss of cofactors of neuron cytochrome c oxidase reversed by estrogen. Exp Neurology 215: 212-219
- Jones TT, Brewer GJ (2010) Age-related deficiencies in Complex I endogenous substrate availability and reserve capacity of Complex IV in cortical neuron electron transport. Biochim Biophys Acta Bioenergetics 1797: 167-176.
- The lab of Gregory Brewer developed techniques for high-resolution respirometry with the OROBOROS-O2k of neuronal cells attached to a substrate:
- In most cases, adherent cells grown as a monolayer are detached from the culture plate (scrapping or trypsinizing), centrifuged and resuspended for HRR.
Appropriate cell density for HRR
- The appropriate cell number is cell type and cell size dependent. The sample concentration should be high enough to get a reliable respiration even when mitochondria have a low respiratory activity. On the other hand, if respiration is too high, re-oxygenations have to be performed frequently disturbing the experimental course. As a general guideline:
- Maximum flux up to 100 to 150 pmol.s-1.ml-1
- Minimum fluxes at 5 pmol.s-1.ml-1
- The appropriate cell number is cell type and cell size dependent. The sample concentration should be high enough to get a reliable respiration even when mitochondria have a low respiratory activity. On the other hand, if respiration is too high, re-oxygenations have to be performed frequently disturbing the experimental course. As a general guideline:
- ROUTINE respiration per cell may depend on cell density:
- Steinlechner-Maran R, Eberl T, Kunc M, Margreiter R, Gnaiger E (1996) Oxygen dependence of respiration in coupled and uncoupled endothelial cells. Am J Physiol Cell Physiol 271:C2053-61. - »Bioblast link«
- ROUTINE respiration per cell may depend on cell density:
Fibroblasts, HUVEC, thymocytes, lymphocytes
- 1.0 million cells/ml is recommended for many cultured cells, including different cancer or immortalized cell lines. A minimum of 0.1 million cells/ml is required.
Hepatocytes
- Isolated hepatocytes are quite large, therefore, 0.1 million cells/ml can be applied.