Spontaneous tension oscillation in skinned bovine cardiac muscle

Norio Fukuda, Hideaki Fujita, Takashi Fujita, Shin'ichi Ishiwata

    Research output: Contribution to journalArticle

    35 Citations (Scopus)

    Abstract

    Skinned fibres from bovine ventricles exhibited spontaneous tension oscillations when MgADP and inorganic phosphate (Pi) were added to the solution bathing fibres in the relaxed state (ADP-SPOC). A similar type of oscillation was observed at intermediate concentrations of free Ca2+ in the absence of MgADP and Pi (Ca-SPOC). To investigate the correlation between ADP-SPOC and Ca-SPOC, we constructed two-dimensional state diagrams of cardiac muscle using different concentrations of Pi (0-20 mM) and free Ca2+ [pCa = around 5 (+Ca2+), pCa = 5.15-6.9 and +EGTA (-Ca2+)], with varying concentrations of MgADP (0-10 mM), with 2 mM MgATP and 2 mM free Mg2+ maintaining ionic strength at 0.15 ± 0.01 M, pH 7.0, 25°C. The three-dimensional (pCa-Pi-MgADP) state diagram thus obtained was divided into three regions, i.e. the contraction region in which tension oscillation was undetectable, the spontaneous tension oscillation (SPOC) region and the relaxation region. We found that the regions of ADP-SPOC and Ca-SPOC were continuously connected by a single oscillation region sandwiched between the contraction and relaxation regions. The state diagram, which encompasses physiological conditions, shows that the probability of SPOC is higher in cardiac muscle than in skeletal muscle. From these results, we suggest that, despite distinct ionic conditions, the molecular state of cross-bridges during SPOC is common to both ADP-SPOC and Ca-SPOC.

    Original languageEnglish
    Pages (from-to)1-8
    Number of pages8
    JournalPflugers Archiv European Journal of Physiology
    Volume433
    Issue number1-2
    DOIs
    Publication statusPublished - 1996

    Keywords

    • Cardiac muscle
    • Oscillation
    • Spontaneous oscillatory contraction
    • Spontaneous tension oscillation
    • State diagram of muscle

    ASJC Scopus subject areas

    • Physiology

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