Cardiac gap junction channel activity in embryonic chick ventricle cells

Area of Science:

• Cardiovascular Physiology
• Cellular Electrophysiology
• Ion Channel Biophysics

Background:

• Gap junctions are crucial for intercellular communication in cardiac tissue.
• Understanding the biophysical properties of cardiac gap junction channels is essential for comprehending heart function and disease.

Purpose of the Study:

• To characterize the single-channel properties of gap junctions in embryonic chick ventricle cells.
• To investigate the factors influencing gap junctional conductance (Gj) and channel activity.

Main Methods:

• Utilized the double whole-cell patch-clamp technique to record single-gap junction-channel currents.
• Analyzed junctional conductance (Gj), single-channel conductance (gamma j), and channel gating kinetics.
• Examined the effects of cell membrane potential, transjunctional potential, 1-octanol, and elevated intracellular calcium ([Cai]) on channel activity.

Main Results:

• Recorded single-channel currents with a main conductance (gamma j) of 166 +/- 51 pS, independent of Gj.
• Observed a secondary conductance level of 60-80 pS in some records.
• Found that channel activity was unaffected by membrane or transjunctional potentials, but open-state probability (Po) and Gj were reversibly reduced by 1-octanol or elevated [Cai].

Conclusions:

• Cardiac gap junction channels exhibit stochastic gating with distinct conductance levels.
• Channel open probability and conductance are modulated by chemical agents like 1-octanol and intracellular calcium.
• The nature of the lower conductance state (subconductance or separate channel) requires further investigation.