Ultrastructural changes in gap junctions associated with CO2 uncoupling in frog atrial fibres

Area of Science:

• Cardiovascular Physiology
• Cell Biology
• Biophysics

Background:

• Gap junctions mediate electrical coupling in cardiac tissue.
• The frog auricle exhibits unique gap junction organization.
• Understanding structure-function relationships in gap junctions is crucial.

Purpose of the Study:

• To investigate the correlation between gap junction morphology and electrical coupling in the frog auricle.
• To elucidate how CO2-induced uncoupling affects gap junction structure.
• To determine the reversibility of morphological changes upon restoration of electrical coupling.

Main Methods:

• Electrical coupling assessed via microelectrode recording and double sucrose gap experiments.
• Tissue fixation with glutaraldehyde followed by freeze-fracture.
• Morphological analysis of gap junctions before, during, and after CO2 perfusion.

Main Results:

• CO2 perfusion induced significant electrical uncoupling (>97%).
• Morphological changes included decreased particle density and increased dispersion of gap junction assemblies.
• Reversible uncoupling was observed, but gap junctions remained smaller after recovery.

Conclusions:

• CO2-induced electrical uncoupling is associated with decreased gap junction organization and particle dispersion.
• Morphological alterations in gap junctions are largely reversible, but some changes persist.
• Findings provide insights into the dynamic nature of gap junctions and their role in electrical coupling.