Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA042

Poster Communications

Ultrastructure and ion channel expression of the Purkinje-ventricular junction in rabbit heart

I. OH1,3, S. Nakao2, T. Starborg3, L. Stuart3, H. Sitpura3, X. Cai3, J. Yanni3, S. Logantha3, C. B. Jones3, A. Vohra3, H. Dobrzynski3, G. Hart3, A. Kitmitto3, M. R. Boyett3

1. Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea (the Republic of). 2. Ritsumeikan University, Shiga, Japan. 3. University of Manchester, Manchester, United Kingdom.

Background: For decades, the Purkinje fibre (PF)-ventricular junction has been implicated in arrhythmogenesis, but it remains an enigmatic and understudied region of the heart. Objective: We aimed to unravel the ultrastructure and ion channel expression of the PF-ventricular junction. Methods: The PF-RV region was excised from 3 rabbit hearts, fixed and stained for serial block face-scanning electron microscopy (SBF-SEM). Megascan 3D datasets for cardiomyocytes (a height of 0.8-mm) were collected over 1 week, with voxel sizes 30, 30, 150 nm in the X, Y, Z directions, respectively. Ion channel expression was measured in the free-running PFs, the junctional region and the ventricular wall of the right ventricle using quantitative PCR. Results: There were two types of cell in the junctional area. One type of cell (J1) was long, large, and rod-shaped and had a 3.7× larger volume and 2.1× larger surface area than free-running PF cells. The other type of cell (J2) was short, wide and had a 2.0× larger volume than free-running PF cells. In addition, the boundary between two junctional cells had numerous wrinkles (like a curtain), which increased the area for the intercalated disc. Ion channel expression of the junctional are was unique, sometimes like that of the PFs, sometimes like that of the ventricular muscle and sometimes different from both tissues (e.g. KvLQT1 was significantly lower in the junctional tissue compared to the PFs and ventricular muscle). Conclusion: As long suspected, there is a distinct junctional tissue with unique properties at the border of the PFs and ventricular muscle. The unique properties of the junctional tissue presumably boost the incoming weak signal of the PFs to allow it to activate the large mass of surrounding ventricular muscle, as well as explaining its role in arrhythmogenesis.

Where applicable, experiments conform with Society ethical requirements