MTT assay

Other closely related tetrazolium dyes including XTT, MTS and the WSTs, are used in conjunction with the intermediate electron acceptor, 1-methoxy phenazine methosulfate (PMS).

[3] However, this traditionally assumed explanation is currently contended as proof has also been found of MTT reduction to formazan in lipidic cellular structures without apparent involvement of oxidoreductases.

[4] Tetrazolium dye assays can also be used to measure cytotoxicity (loss of viable cells) or cytostatic activity (shift from proliferation to quiescence) of potential medicinal agents and toxic materials.

Precautions are needed to ensure accuracy when using this assay and there are strong arguments for confirming MTS results using qualitative observations under a microscope.

[11] Tetrazolium dye reduction is generally assumed to be dependent on NAD(P)H-dependent oxidoreductase enzymes largely in the cytosolic compartment of the cell.

It is important to keep in mind that assay conditions can alter metabolic activity and thus tetrazolium dye reduction without affecting cell viability.

[4] Nevertheless, even under this alternative paradigm, MTT assay still assesses the reduction potential of a cell (i.e. availability of reducing compounds to drive cellular energetics).