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Related Experiment Videos

Ionic movements and irreversible anoxic damage.

R A Altschuld, W C Wenger, G P Brierley

    Basic Research in Cardiology
    |January 1, 1985
    PubMed
    Summary
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    Cardiologia (Rome, Italy)·1998

    Myocyte hypercontracture, a cellular change, can be triggered by calcium or ATP levels. Researchers found that high ATP levels in myocytes can lead to calcium-dependent hypercontracture, even without external calcium.

    Area of Science:

    • Cellular Biology
    • Muscle Physiology
    • Biochemistry

    Background:

    • Myocyte hypercontracture, a significant cellular alteration, can be induced by calcium addition to calcium-intolerant cells.
    • Similar changes occur in calcium-free media under conditions like reoxygenation of anoxic, ATP-depleted myocytes or digitonin permeabilization of respiring myocytes.

    Purpose of the Study:

    • To investigate the mechanisms underlying myocyte hypercontracture in calcium-free environments.
    • To examine the specific roles of magnesium adenosine triphosphate (MgATP), free calcium (pCa), and cellular respiration in inducing hypercontracture.

    Main Methods:

    • Utilized rotenone-treated, digitonin-permeabilized myocytes to isolate and study hypercontracture.
    • Manipulated MgATP concentrations (0.1-10 mM) and pCa levels (pCa 8.5 to 4.5) in the presence and absence of succinate (respiration substrate).

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    Main Results:

    • In calcium-free conditions (pCa 8.5), hypercontracture was observed at low MgATP concentrations (<1 mM) but was prevented by higher MgATP levels (>1 mM).
    • At elevated MgATP levels (1-10 mM), hypercontracture became dependent on the presence of calcium.
    • Succinate addition promoted Ca2+-independent hypercontracture at lower ATP regeneration levels by supporting respiration.

    Conclusions:

    • Myocyte hypercontracture is influenced by the interplay between ATP levels and calcium availability.
    • High intracellular ATP can promote calcium-dependent hypercontracture, while lower ATP levels may facilitate calcium-independent contraction under specific conditions.
    • Cellular respiration plays a role in modulating ATP levels and thus influences the conditions under which hypercontracture occurs.