Sodium channel distribution within the rabbit atrioventricular node as analysed by confocal microscopy

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Electrophysiology

Background:

• Sodium channels are crucial for cardiac impulse conduction.
• Connexin43 forms gap junctions, essential for cell-to-cell communication in the heart.
• The specific distribution of these proteins in the atrioventricular node is not fully understood.

Purpose of the Study:

• To investigate the spatial distribution of sodium channels and connexin43 within the rabbit atrioventricular node.
• To correlate protein expression patterns with functional properties of AV nodal conduction.

Main Methods:

• Immunohistochemistry and confocal microscopy were used on rabbit AV nodal tissue.
• Antibodies against sodium channels (interdomain 3-4 region) and connexin43 (carboxyl terminus) were employed.
• Immunofluorescence was quantified and localized within different AV nodal cell populations.

Main Results:

• Sodium channels and connexin43 were abundant in atrial and ventricular myocardium, localized to membranes and T-tubules (sodium channels) and intercalated discs (connexin43).
• In the AV node, peripheral transitional cells showed high expression, similar to myocardium.
• Central midnodal cells exhibited significantly reduced or absent sodium channel and connexin43 immunofluorescence.

Conclusions:

• A gradient of sodium channel and connexin43 expression exists within the rabbit AV node.
• The paucity of these proteins in the central AV node suggests a mechanism for slowed impulse conduction.
• This differential expression pattern is critical for the unique electrophysiological properties of the AV node.