Membrane potential estimation by flow cytometry

Area of Science:

• Cellular biology
• Biophysics

Background:

• Membrane potential (delta psi) is established by ion gradients and is vital for transmembrane signaling in many cell types.
• Changes in delta psi are linked to cell development, function, pathology, and membrane integrity, particularly in bacteria lacking mitochondria.
• Mitochondrial delta psi is a key indicator of cellular energy metabolism and is disrupted during apoptosis.

Purpose of the Study:

• To review the role and measurement of membrane potential (delta psi) in various biological contexts.
• To discuss the utility of flow cytometry for assessing delta psi in eukaryotic cells, mitochondria, and bacteria.
• To highlight the limitations and necessary controls for accurate delta psi measurement.

Main Methods:

• Utilizes flow cytometry for estimating membrane potential.
• Employs lipophilic cationic and anionic dyes (e.g., cyanines, rhodamine 123, oxonols) for detecting changes in delta psi.
• Incorporates newer ratiometric techniques for precise delta psi quantification.

Main Results:

• Older dye-based methods detect large delta psi changes and population heterogeneity.
• Newer ratiometric techniques enable precise delta psi measurement within 10 mV.
• Identifies potential confounding factors affecting fluorescence measurements, such as efflux pumps and medium composition.

Conclusions:

• Accurate estimation and measurement of delta psi require careful control of experimental conditions.
• Flow cytometry is a versatile tool for assessing membrane potential across different cell types and conditions.
• Understanding delta psi is critical for interpreting cellular signaling, metabolism, and integrity.