Background:

Tetramethylrhodamine methyl ester (TMRM) (perchlorate) is a non-cytotoxic cell-permeant fluorogenic dye most commonly used to assess mitochondrial function using live cell fluorescence microscopy and flow cytometry.1,2,3 It has two excitation peaks at 515 and 555 nm and an emission peak in the red-orange range (575 nm). Due to the polarization of the mitochondrial membrane, TMRM is taken up into healthy mitochondria. However, when the membrane is depolarized, as in apoptosis, it is not taken up or is released from the mitochondria. Thus, the strength of the fluorescence signal in mitochondria is used to assess cell viability.

Reference:?

1. Farkas, D.L., Wei, M.-d., Febbroriello, P., et al. Simultaneous imaging of cell and mitochondrial membrane potentials Biophys J. 56(6), 1053-1069 (1989).
2. Gandra, P.G., Nogueira, L., and Hogan, M.C. Mitochondrial activation at the onset of contractions in isolated myofibres during successive contractile periods J. Physiol. 590(15), 3597-3609 (2012).
3. Michea, L., Combs, C., Andrews, P., et al. Mitochondrial dysfunction is an early event in high-NaCl-induced apoptosis of mIMCD3 cells Am. J. Physiol. Renal Physiol. 282(6), F981-F990 (2002).