Published Online
on April 2, 2009

A more recent version of this article appeared on June 1, 2009

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Original Article

Ion channel transcript expression at the rabbit atrioventricular conduction axis

Ian D. Greener¹; James O. Tellez¹; Halina Dobrzynski¹; Mitsuru Yamamoto²; Gillian M. Graham³; Rudi Billeter⁴ and Mark Boyett^1,5

¹ University of Manchester, Manchester, United Kingdom;
² Reseach Inst. of Environmental Med., Nagoya University, Nagoya, Japan;
³ University of Leeds, Leeds, United Kingdom;
⁴ University of Nottingham, Nottingham, United Kingdom

⁵ E-mail: mark.boyett{at}manchester.ac.uk

Background—Little is known about the distribution of gap junctions and ion channels in the atrioventricular node (AVN), even though the physiology and pathology of the AVN is ultimately dependent on them.

Methods and Results—The abundance of 30 transcripts for markers, gap junctions, ion channels and Ca²⁺ handling proteins in different regions of the rabbit AVN (nodal extension and proximal and distal penetrating bundle of His as well as atrial and ventricular muscle) was measured using a novel quantitative PCR technique and in situ hybridisation. The expression profile of the nodal extension (slow pathway into penetrating bundle) was similar to that of the sinoatrial node: for example, in the nodal extension, in contrast to the atrial muscle and as expected for a slowly conducting tissue with pacemaker activity, there was no or reduced expression of Cx43, Na_v1.5, Ca_v1.2, K_v1.4, KChIP2 and RYR3 and high expression of Ca_v1.3 and HCN4. The expression profile of the penetrating bundle was less specialised. In situ hybridisation revealed a transitional zone with reduced expression of Cx43, Na_v1.5 and KChIP2 that may form the fast pathway into the penetrating bundle.

Conclusions—At the AVN, the expression of gap junctions and ion channels in the nodal extension (slow pathway) and a transitional zone (putative fast pathway) as well as the penetrating bundle (output pathway) is specialised and heterogeneous and roughly matches the electrophysiology of the different regions.

Key Words: atrioventricular node • ion channels • polymerase chain reaction • conduction system • connexins

Author contributions: Rudi Billeter and Mark R. Boyett are joint senior authors.