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Mitochondrial health is an indicator of overall cell health

Healthy mitochondria exhibit a difference in electrical potential across the lipid bilayer that surrounds them, and some fluorescent dyes will accumulate inside mitochondria as long as this potential difference is maintained.

Learn about TMRM, a dye that localizes to the mitochondria.

Labeling functioning mitochondria

Mitochondria are organelles found in every eukaryotic cell. Because they generate ATP, they can be thought of as the power plants of the cell. In addition to energy production, mitochondria also play critical roles in cell signaling, cell cycle, calcium buffering, and both cell growth and death.

The ATP generation machinery and compartments housing other specialized functions are all maintained within the mitochondrion by a phospholipid bilayer. Healthy mitochondrial membranes maintain a difference in electric potential between the interior and exterior of the organelle, referred to as the membrane potential. This membrane potential is a direct result of mitochondrial functional processes, and can be lost if the mitochondria are not working properly. And, if the mitochondria are not functional, it’s a pretty good bet that the cells are not healthy either.

There are several fluorescent dyes available for the specific labeling of mitochondria. Dyes whose accumulation and localization to the mitochondria depend on mitochondrial membrane potential can be a useful indicator of cell health. In healthy cells where mitochondrial membrane potential is present, you will see a bright fluorescent signal, but in cells that have lost their mitochondrial membrane potential, you will see a dim (or sometimes no) fluorescent signal.


Illustration of a mitochondrion, with charge differences on the inside vs the outside of the membrane indicated.

Figure 1. Illustration of a mitochondrion. The electric potential, noted as ΔΨ, is lost in non-functional mitochondria.

Tetramethylrhodamine, methyl ester (TMRM) is a cell-permeant dye that accumulates in active mitochondria with intact membrane potentials. If the cells are healthy and have functioning mitochondria, the signal will be bright. Upon loss of the mitochondrial membrane potential, TMRM accumulation will cease and the signal will dim or disappear.

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