Voltage-dependent capacitance of human embryonic kidney cells

Area of Science:

• Biophysics
• Cellular Electrophysiology
• Membrane Biophysics

Background:

• Membrane capacitance (C) is a critical parameter in understanding cell electrophysiology.
• Voltage-dependent capacitance changes are observed in various cell types, including outer hair cells (OHCs).
• The role of electromechanical coupling in membrane capacitance is an area of ongoing research.

Purpose of the Study:

• To determine the voltage dependence of membrane capacitance in human embryonic kidney (HEK) cells.
• To investigate the influence of salicylate on membrane capacitance and its voltage relationship.
• To explore the potential contribution of electromechanical coupling to observed capacitance changes.

Main Methods:

• Whole-cell patch-clamp configuration was used to measure current in HEK cells.
• A dual-sinusoidal stimulus was applied to determine admittance (Y) and calculate capacitance (C).
• Voltage ramps were performed with and without sodium salicylate in the extracellular solution.

Main Results:

• Membrane capacitance (C) showed a small increase (<1%) with the square of the applied voltage (Psi).
• Salicylate reduced membrane charge asymmetry but did not alter the rate of capacitance increase with voltage.
• An additional linear differential capacitance was observed in some cells, absent with salicylate, suggesting electromechanical coupling (e.g., electrostriction, Maxwell stress).

Conclusions:

• Voltage-dependent capacitance in HEK cells arises from electromechanical coupling, with an estimated force of ~1 pN.
• The charge contribution from collective membrane protein and lipid motion is significantly less than in prestin-expressing cells.
• Capacitance-voltage relationships in non-prestin OHCs are likely similar to those observed in HEK cells.