Spontaneous oscillatory contraction (SPOC) in cardiomyocytes

Tatsuya Kagemoto, Amy Li, Cris dos Remedios, Shin’ichi Ishiwata

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    SPOC (spontaneous oscillatory contraction) is a characteristic state of the contractile system of striated (skeletal and cardiac) muscle that exists between the states of relaxation and contraction. For example, Ca-SPOCs occur at physiological Ca2+ levels (pCa ∼6.0), whereas ADP-SPOC occurs in the virtual absence of Ca2+ (pCa ≥ 8; relaxing conditions in the presence of MgATP), but in the presence of inorganic phosphate (Pi) and a high concentration of MgADP. The concentration of Mg-ADP necessary for SPOC is nearly equal to or greater than the MgATP concentration for cardiac muscle and is several times higher for skeletal muscle. Thus, the cellular conditions for SPOC are broader in cardiac muscle than in skeletal muscle. During these SPOCs, each sarcomere in a myofibril undergoes length oscillation that has a saw-tooth waveform consisting of a rapid lengthening and a slow shortening phase. The lengthening phase of one half of a sarcomere is transmitted to the adjacent half of the sarcomere successively, forming a propagating wave (termed a SPOC wave). The SPOC waves are synchronized across the cardiomyocytes resulting in a visible wave of successive contractions and relaxations termed the SPOC wave. Experimentally, the SPOC period (and therefore the velocity of SPOC wave) is observed in demembranated cardiomyocytes and can be prepared from a wide range of animal hearts. These periods correlate well with the resting heartbeats of a wide range of mammals (rat, rabbit, dog, pig and cow). Preliminary experiments showed that the SPOC properties of human cardiomyocytes are similar to the heartbeat of a large dog or a pig. This correlation suggests that SPOCs may play a fundamental role in the heart. Here, we briefly summarize a range of SPOC parameters obtained experimentally, and relate them to a theoretical model to explain those characteristics. Finally, we discuss the possible significance of these SPOC properties in each and every heartbeat.

    Original languageEnglish
    Pages (from-to)15-24
    Number of pages10
    JournalBiophysical Reviews
    Volume7
    Issue number1
    DOIs
    Publication statusPublished - 2015

    Fingerprint

    Sarcomeres
    Cardiac Myocytes
    Adenosine Diphosphate
    Myocardium
    Skeletal Muscle
    Swine
    Adenosine Triphosphate
    Dogs
    Myofibrils
    Mammals
    Tooth
    Theoretical Models
    Phosphates
    Rabbits

    Keywords

    • Cardiomyocytes
    • Heartbeat
    • Sarcomere
    • SPOC
    • SPOC wave
    • Spontaneous oscillatory contraction

    ASJC Scopus subject areas

    • Biophysics
    • Molecular Biology
    • Structural Biology

    Cite this

    Kagemoto, T., Li, A., dos Remedios, C., & Ishiwata, S. (2015). Spontaneous oscillatory contraction (SPOC) in cardiomyocytes. Biophysical Reviews, 7(1), 15-24. https://doi.org/10.1007/s12551-015-0165-7

    Spontaneous oscillatory contraction (SPOC) in cardiomyocytes. / Kagemoto, Tatsuya; Li, Amy; dos Remedios, Cris; Ishiwata, Shin’ichi.

    In: Biophysical Reviews, Vol. 7, No. 1, 2015, p. 15-24.

    Research output: Contribution to journalArticle

    Kagemoto, T, Li, A, dos Remedios, C & Ishiwata, S 2015, 'Spontaneous oscillatory contraction (SPOC) in cardiomyocytes', Biophysical Reviews, vol. 7, no. 1, pp. 15-24. https://doi.org/10.1007/s12551-015-0165-7
    Kagemoto, Tatsuya ; Li, Amy ; dos Remedios, Cris ; Ishiwata, Shin’ichi. / Spontaneous oscillatory contraction (SPOC) in cardiomyocytes. In: Biophysical Reviews. 2015 ; Vol. 7, No. 1. pp. 15-24.
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