Equilibrium properties of a voltage-dependent junctional conductance

Area of Science:

• Developmental Biology
• Cell Biology
• Biophysics

Background:

• Gap junctions facilitate direct cell-to-cell communication in early embryonic development.
• Understanding the regulation of gap junction conductance is crucial for comprehending developmental processes.

Purpose of the Study:

• To investigate the voltage dependence of junctional conductance between amphibian blastomeres.
• To elucidate the biophysical mechanisms underlying this voltage sensitivity.

Main Methods:

• Voltage clamp experiments were performed on isolated pairs of amphibian blastomeres (Ambystoma mexicanum, Xenopus laevis, Rana pipiens).
• Junctional current was measured during transjunctional voltage steps to determine conductance changes.

Main Results:

• Steady-state junctional conductance decreased sharply with increasing transjunctional voltage of either polarity.
• A small, voltage-insensitive conductance persisted at high voltages.
• The conductance changes were modeled by a reversible two-state system, implying movement of approximately six electron charges.

Conclusions:

• Gap junctional conductance in early amphibian embryos is strongly voltage-dependent.
• The findings support the hypothesis that gap junction intramembrane particles act as voltage-sensitive channels.