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Contraction features in normal and hypodynamic lizard ventricle

L Cedrini, E Camino, G Alloatti

    Journal De Physiologie
    |March 1, 1981
    PubMed
    Summary
    This summary is machine-generated.

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    Hypodynamia in lizard ventricles involves altered calcium handling, shifting the strength-interval relationship and affecting electrical activity. Restoring calcium levels normalizes heart function, suggesting calcium flux is key to twitch tension.

    Area of Science:

    • Cardiology
    • Comparative Physiology
    • Cellular Electrophysiology

    Background:

    • Cardiac muscle function is regulated by intracellular calcium.
    • Understanding the mechanisms of cardiac contractility in non-mammalian vertebrates provides insights into fundamental physiological processes.

    Purpose of the Study:

    • To investigate the electrophysiological and mechanical changes in lizard ventricles during hypodynamia.
    • To elucidate the role of calcium ions in regulating ventricular contractility and the strength-interval relationship.

    Main Methods:

    • Recording isometric twitches and electrical activity from lizard ventricles at various driving rates.
    • Inducing hypodynamia by high-flow perfusion and assessing recovery with altered calcium concentrations.
    • Examining ventricular ultrastructure using electron microscopy.

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    Main Results:

    • Hypodynamia shifted the steady-state strength-interval relationship to higher stimulation rates.
    • Perfusion with calcium-rich solutions restored the normal strength-interval relationship in hypodynamic ventricles.
    • Hypodynamic state showed increased action potential duration, decreased maximal rate of pressure development, and altered staircase responses, despite preserved ultrastructure.

    Conclusions:

    • Twitch tension in lizard ventricles is influenced by two calcium ion fluxes: one from intracellular stores and another related to action potential duration.
    • A cellular calcium store is hypothesized to exist in the lizard ventricle, facilitating rapid calcium release.
    • Hypodynamia may result from reduced calcium affinity of this store and decreased calcium influx during the action potential plateau.