Comparative measurements of membrane potentials with microelectrodes and voltage-sensitive dyes

Area of Science:

• Cellular electrophysiology
• Fluorescent dye technology

Background:

• Accurate measurement of cell membrane potential is crucial for understanding cellular function.
• Existing voltage-sensitive dyes may have limitations in specific applications.

Purpose of the Study:

• To evaluate the utility of the novel voltage-sensitive fluorescent dye, diBA-C4-(3)-, for measuring cell membrane potential.
• To characterize the dye's response kinetics and reliability in cellular models.

Main Methods:

• Utilized BICR/M1R-k and L cells, fused into giant homokaryons using polyethyleneglycol.
• Simultaneously measured membrane potential with glass microelectrodes and recorded diBA-C4-(3)- fluorescence.
• Manipulated membrane potential via bicarbonate concentration changes and voltage clamping.

Main Results:

• The dye diBA-C4-(3)- exhibited a fluorescence response of approximately 1% per mV.
• Mathematical analysis indicated a first-order reaction for fluorescence changes, with rate constants ranging from 0.1 to 0.8 min⁻¹.
• Cell size, determined by nuclei count in homokaryons, influenced the dye's response rate.

Conclusions:

• The voltage-sensitive oxonol dye diBA-C4-(3)- is a useful tool for assessing cell membrane potential.
• The dye's response kinetics are dependent on cell size, providing insights into its mechanism.
• This study proposes a model to explain the observed fluorescence changes.