Atrioventricular Bundle

2020 ◽  
Author(s):  
Keyword(s):  
Atrioventricular Bundle

The spatial distribution and relative abundance of gap-junctional connexin40 and connexin43 correlate to functional properties of components of the cardiac atrioventricular conduction system

1993 ◽  
Vol 105 (4) ◽  
pp. 985-991 ◽  
Author(s):  
R.G. Gourdie ◽  
N.J. Severs ◽  
C.R. Green ◽  
S. Rothery ◽  
P. Germroth ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Relative Abundance ◽  
Atrioventricular Node ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Purkinje Fibre ◽  
Purkinje Fibres ◽  
Atrioventricular Bundle ◽  
Junctional Protein ◽  
Gap Junctional

Electrical coupling between heart muscle cells is mediated by specialised regions of sarcolemmal interaction termed gap junctions. In previous work, we have demonstrated that connexin42, a recently identified gap-junctional protein, is present in the specialised conduction tissues of the avian heart. In the present study, the spatial distribution of the mammalian homologue of this protein, connexin40, was examined using immunofluorescence, confocal scanning laser microscopy and quantitative digital image analysis in order to determine whether a parallel distribution occurs in rat. Connexin40 was detected by immunofluorescence in all main components of the atrioventricular conduction system including the atrioventricular node, atrioventricular bundle, and Purkinje fibres. Quantitation revealed that levels of connexin40 immunofluorescence increased along the axis of atrioventricular conduction, rising over 10-fold between atrioventricular node and atrioventricular bundle and a further 10-fold between atrioventricular bundle and Purkinje fibres. Connexin40 and connexin43, the principal gap-junctional protein of the mammalian heart, were co-localised within atrioventricular nodal tissues and Purkinje fibres. By applying a novel photobleach/double-labelling protocol, it was demonstrated that connexin40 and connexin43 are co-localised in precisely the same Purkinje fibre myocytes. A model, integrating data on the spatial distribution and relative abundance of connexin40 and connexin43 in the heart, proposes how myocyte-type-specific patterns of connexin isform expression account for the electrical continuity of cardiac atrioventricular conduction.

scholarly journals Specialized impulse conduction pathway in the alligator heart

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Bjarke Jensen ◽  
Bastiaan J Boukens ◽  
Dane A Crossley ◽  
Justin Conner ◽  
Rajiv A Mohan ◽  
...  
Keyword(s):  
Conduction System ◽  
Atrioventricular Conduction ◽  
Alligator Mississippiensis ◽  
Ventricular Septum ◽  
Heart Rates ◽  
Conduction Pathway ◽  
Atrioventricular Bundle ◽  
Rapid Activation ◽  
Ventricular Conduction ◽  
Purkinje Network

Mammals and birds have a specialized cardiac atrioventricular conduction system enabling rapid activation of both ventricles. This system may have evolved together with high heart rates to support their endothermic state (warm-bloodedness) and is seemingly lacking in ectothermic vertebrates from which first mammals then birds independently evolved. Here, we studied the conduction system in crocodiles (Alligator mississippiensis), the only ectothermic vertebrates with a full ventricular septum. We identified homologues of mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb) and show the presence of a functional atrioventricular bundle. The ventricular Purkinje network, however, was absent and slow ventricular conduction relied on trabecular myocardium, as it does in other ectothermic vertebrates. We propose the evolution of the atrioventricular bundle followed full ventricular septum formation prior to the development of high heart rates and endothermy. In contrast, the evolution of the ventricular Purkinje network is strongly associated with high heart rates and endothermy.

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