Ultrastructure of primary pacemaking cells in rabbit sino-atrial node cells indicates limited sarcoplasmic reticulum content.
gap junctions
pacemaker cells
sarcoplasmic reticulum
sino‐atrial node
Journal
FASEB bioAdvances
ISSN: 2573-9832
Titre abrégé: FASEB Bioadv
Pays: United States
ID NLM: 101733210
Informations de publication
Date de publication:
Feb 2020
Feb 2020
Historique:
received:
20
12
2018
revised:
20
12
2018
accepted:
25
11
2019
entrez:
4
3
2020
pubmed:
4
3
2020
medline:
4
3
2020
Statut:
epublish
Résumé
The main mammalian heart pacemakers are spindle-shaped cells compressed into tangles within protective layers of collagen in the sino-atrial node (SAN). Two cell types, "dark" and "light," differ on their high or low content of intermediate filaments, but share scarcity of myofibrils and a high content of glycogen. Sarcoplasmic reticulum (SR) is scarce. The free SR (fSR) occupies 0.04% of the cell volume within ~0.4 µm wide peripheral band. The junctional SR (jSR), constituting peripheral couplings (PCs), occupies 0.03% of the cell volume. Total fSR + jSR volume is 0.07% of cell volume, lower than the SR content of ventricular myocytes. The average distance between PCs is 7.6 µm along the periphery. On the average, 30% of the SAN cells surfaces is in close proximity to others. Identifiable gap junctions are extremely rare, but small sites of close membrane-to-membrane contacts are observed. Possibly communication occurs via these very small sites of contact if conducting channels (connexons) are located within them. There is no obvious anatomical detail that might support ephaptic coupling. These observations have implications for understanding of SAN cell physiology, and require incorporation into biophysically detailed models of SAN cell behavior that currently do not include such features.
Identifiants
pubmed: 32123860
doi: 10.1096/fba.2018-00079
pii: FBA21104
pmc: PMC7003656
doi:
Types de publication
Journal Article
Langues
eng
Pagination
106-115Informations de copyright
© 2019 The Authors.
Déclaration de conflit d'intérêts
The authors have no conflicts of interest.
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