Variability in timing of spontaneous calcium release in the intact rat heart is determined by the time course of sarcoplasmic reticulum calcium load

J. Andrew Wasserstrom, Yohannes Shiferaw, Wei Chen, Satvik Ramakrishna, Heetabh Patel, James E. Kelly, Matthew J. O'Toole, Amanda Pappas, Nimi Chirayil, Nikhil Bassi, Lisa Akintilo, Megan Wu, Rishi Arora, Gary L. Aistrup

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

Background: Abnormalities in intracellular calcium (Ca) cycling during Ca overload can cause triggered activity because spontaneous calcium release (SCR) activates sufficient Ca-sensitive inward currents to induce delayed afterdepolarizations (DADs). However, little is known about the mechanisms relating SCR and triggered activity on the tissue scale. Methods and Results: Laser scanning confocal microscopy was used to measure the spatiotemporal properties of SCR within large myocyte populations in intact rat heart. Computer simulations were used to predict how these properties of SCR determine DAD magnitude. We measured the average and standard deviation of the latency distribution of SCR within a large population of myocytes in intact tissue. We found that as external [Ca] is increased, and with faster pacing rates, the average and SD of the latency distribution decreases substantially. This result demonstrates that the timing of SCR occurs with less variability as the sarcoplasmic reticulum (SR) Ca load is increased, causing more sites to release Ca within each cell. We then applied a mathematical model of subcellular Ca cycling to show that a decrease in SCR variability leads to a higher DAD amplitude and is dictated by the rate of SR Ca refilling following an action potential. Conclusions: Our results demonstrate that the variability of the timing of SCR in a population of cells in tissue decreases with SR load and is dictated by the time course of the SR Ca content.

Original languageEnglish (US)
Pages (from-to)1117-1126
Number of pages10
JournalCirculation research
Volume107
Issue number9
DOIs
StatePublished - Oct 29 2010

Keywords

  • Ca sparks
  • Ca transients
  • arrhythmia
  • sarcoplasmic reticulum

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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    Wasserstrom, J. A., Shiferaw, Y., Chen, W., Ramakrishna, S., Patel, H., Kelly, J. E., O'Toole, M. J., Pappas, A., Chirayil, N., Bassi, N., Akintilo, L., Wu, M., Arora, R., & Aistrup, G. L. (2010). Variability in timing of spontaneous calcium release in the intact rat heart is determined by the time course of sarcoplasmic reticulum calcium load. Circulation research, 107(9), 1117-1126. https://doi.org/10.1161/CIRCRESAHA.110.229294