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Updated: Jun 25, 2025

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
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Observation of sarcomere chaos induced by changes in calcium concentration in cardiomyocytes

Seine A Shintani1,2,3

  • 1Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi 487-8501, Japan.

Biophysics and Physicobiology
|May 28, 2024
PubMed

Insights

Calcium fluctuations induce chaotic instability in sarcomeres during hyperthermal oscillations (HSOs), a phenomenon termed Sarcomere Chaos with Changes in Calcium Concentration (S4C). This instability is crucial for rapid ventricular diastole in heartbeats.

Area of Science:

  • Cardiovascular Physiology
  • Biophysics
  • Cell Biology

Background:

  • Cardiomyocytes exhibit hyperthermal sarcomeric oscillations (HSOs) when heated (38-42°C), characterized by both chaotic instability and homeostatic stability.
  • These oscillations are hypothesized to be vital for the rapid ventricular expansion during cardiac diastole.

Purpose of the Study:

  • To investigate the role of calcium concentration fluctuations in sarcomeric instability during HSOs.
  • To characterize the phenomenon of chaotic sarcomere instability induced by calcium changes and its physiological relevance.

Main Methods:

  • Induction of HSOs in cardiomyocytes via controlled heating.
  • Analysis of sarcomere dynamics under varying calcium concentrations.
  • Measurement of oscillation amplitude and Lyapunov exponent to quantify instability.

Main Results:

  • Calcium concentration fluctuations were found to induce chaotic instability in HSOs, distinct from oscillations under constant calcium.
  • This calcium-induced chaotic instability was named Sarcomere Chaos with Changes in Calcium Concentration (S4C).
  • S4C exhibits fluctuations in oscillation amplitude and a positive Lyapunov exponent, similar to HSOs, and was observed in electro-mechanical coupling relaxation dynamics.

Conclusions:

  • S4C represents a significant sarcomeric property contributing to the dynamic flexibility required for ventricular diastole.
  • Understanding S4C provides insight into the physiological function of sarcomeres, particularly their response to calcium signaling during the cardiac cycle.

Keywords:
contraction rhythm homeostasisexcitation–contraction couplinghyperthermal sarcomeric oscillationssarcomere chaos

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