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Myocardial cell heterogeneity in the human heart with respect to myosin ATPase activity

L E Thornell, S Forsgren

    The Histochemical Journal
    |May 1, 1982
    PubMed

    Insights

    Human heart myosin ATPase activity varies significantly across different cardiac tissues and even within them. This suggests diverse fiber types contribute to the heart's contractile properties.

    Area of Science:

    • Biochemistry
    • Cardiology
    • Molecular Biology

    Background:

    • The Ca2+-activated myosin ATPase is crucial for cardiac muscle contraction.
    • Understanding its properties in different human heart tissues is essential for cardiac physiology.

    Purpose of the Study:

    • To investigate the pH sensitivity of Ca2+-activated myosin ATPase in human atrial, ventricular, and conduction tissues.
    • To identify heterogeneity in ATPase activity within these cardiac regions.

    Main Methods:

    • Enzyme kinetic assays were performed to measure Ca2+-activated myosin ATPase activity.
    • Studies were conducted across a range of pH values.
    • Comparisons were made between atrial, ventricular, and conduction system tissues.

    Main Results:

    • Significant pH sensitivity of Ca2+-activated myosin ATPase was observed in all investigated human heart tissues.
    • Heterogeneity in ATPase activity was found not only between atrial, ventricular, and conduction tissues but also within each of these regions.
    • Variations were noted within ordinary atrial and ventricular myocardium, as well as within the conduction system.

    Conclusions:

    • The observed heterogeneity in ATPase activity is linked to myosin molecule polymorphism.
    • These findings suggest the co-existence of cardiac muscle fiber types with distinct contractile properties in the human heart.

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