Altered ion channel conductance and ionic selectivity induced by large imposed membrane potential pulse

Area of Science:

• Biophysics
• Neuroscience
• Cellular Physiology

Background:

• Voltage-gated ion channels (Na+ and K+) are crucial for muscle and nerve function.
• Electrical shock can cause cellular damage, but the specific effects on ion channels are not fully understood.

Purpose of the Study:

• To investigate the impact of large transmembrane potential pulses on voltage-gated Na+ and K+ channels in frog skeletal muscle.
• To differentiate between electroconformational damage to channels and electroporation of the lipid bilayer.

Main Methods:

• Utilized a modified double vaseline-gap voltage clamp technique.
• Applied 4 ms transmembrane potential pulses of -600 mV to frog skeletal muscle membrane.
• Analyzed changes in ion channel conductivity, selectivity, and binding kinetics.

Main Results:

• A -600 mV pulse significantly reduced both Na+ and K+ channel conductivities.
• Supraphysiologic pulses decreased K+ channel selectivity for K+ over Na+, causing membrane depolarization.
• Tetrodotoxin (TTX) and tetraethylammonium (TEA) binding remained unaffected.
• The rate of recovery from electroconformational damage depended on the magnitude of the applied potential pulse.

Conclusions:

• Large electrical pulses induce electroconformational damage to voltage-gated ion channels.
• This damage affects channel conductivity and selectivity, potentially leading to membrane depolarization.
• Electrocofmormational damage to ion channels may be a contributing factor to muscle and nerve dysfunction following electrical shock.