Synergistic dual automaticity in sinoatrial node cell and tissue models

Hong Zhang, Boyoung Joung, Tetsuji Shinohara, Xi Mei, Peng Sheng Chen, Shien-Fong Lin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Background: The mechanism of sinoatrial node (SAN) automaticity is traditionally attributed to membrane ion currents. Recent evidence indicates spontaneous sarcoplasmic reticulum (SR) Ca 2+ cycling also plays an important role. Methods and Results: A computer simulation on SAN cell and 1D tissue model was performed. In the SAN cells, SR Ca 2+ cycling broadly modulated the sinus rate from 1.74 Hz to 3.87 Hz. Shortening of the junctional SR refilling time and increase of SR Ca 2+ release were responsible for sinus rate acceleration. However, under the fast SR Ca 2+ cycling, decreased L-type Ca 2+ current (ICaL) resulted in irregular firing. When Ca 2+ cycling was suppressed, If and ICaT both acted to stabilize the pacemaker rhythm, but ICaT had less effect than If. At the 1D level, the electrical coupling between neighboring cells had little effect on the earliest pacemaker location. The leading pacemaking site always colocalized with the site with the highest SR Ca 2+ cycling rate, but shifted to the site with less inhibited ICaL. Conclusions: The rate of SR Ca 2+ cycling can effectively and broadly modulate the sinus rate. If, ICaL and ICaT play integral roles to guarantee SAN cell rhythmic firing. The leading pacemaker site is determined by intracellular Ca 2+ dynamics and membrane currents, indicating the synergistic dual automaticity not only exists in single SAN cells, but also at the tissue level.

Original languageEnglish
Pages (from-to)2079-2088
Number of pages10
JournalCirculation Journal
Issue number10
StatePublished - 25 Oct 2010


  • Calcium
  • Ion channels
  • Sarcoplasmic reticulum
  • Sinoatrial node

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