Do human sinoatrial node cells have t-tubules?

• Main Authors: Maria A. Petkova (Author), Halina Dobrzynski (Author)
• Format: Book
• Published: Elsevier, 2021-11-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Every heartbeat is generated by spontaneously depolarizing specialised nodal cells that make up the sinoatrial node (SN). The SN's unique properties depend on two complex mechanisms - the membrane-voltage and the Ca2+ clocks, regulated by strictly defined expression of ion channels, connexins and Ca2+-handling proteins. In the working myocardium these proteins are accumulated in specialised membrane structures- the transverse tubules (t-tubules). It is well known that small mammals do not exhibit t-tubules in their atrium, but such structures are observed in the atria of bigger mammals such as sheep. No information on t-tubules in the human SN is present yet. The aim of our study was to determine if t-tubules are present in the human SN, as well as surrounding atrial myocardium. Dystrophin (cytoplasmic protein connecting the muscle fibres to the surrounding extracellular membrane), Na+-Ca2+ exchanger (NCX1), sarcoplasmic-endoplasmic reticulum calcium adenosine triphosphatase (SERCA2a), α-actinin, and ryanodine receptor 2 (RyR2) were investigated. Staining with wheat germ agglutinin (WGA, specific marker of t-tubules) demonstrated that human RA cells contain t-tubules, but these structures are very sparse in the SN. Experiments in single nodal cells from rat and mouse showed no expression of t-tubular network, but striated pattern of expression of RyR2 was obtained similar to the human sections, suggesting its manner of organization is dependent on α-actinin colocalization.

Item Description

2214-854X
10.1016/j.tria.2021.100131