Maintained contractile reserve in a transgenic mouse model of myocardial stunning

Harald Kögler, David G. Soergel, Anne M. Murphy, Eduardo Marbán

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Cardiac excitation-contraction (E-C) coupling is impaired at the myofilament level in the reversible postischemic dysfunction known as "stunned" myocardium. We characterized tension development and calcium cycling in intact isolated trabeculae from transgenic (TG) mice expressing the major proteolytic degradation fragment of troponin I (TnI) found in stunned myocardium (TnI1-193) and determined the ATPase activity of myofibrils extracted from TG and non-TG mouse hearts. The phenotype of these mice at baseline recapitulates that of stunning. Here, we address the question of whether contractile reserve is preserved in these mice, as it is in genuine stunned myocardium. During twitch contractions, calcium cycling was normal, whereas tension was greatly reduced, compared with non-TG controls. A decrease in maximum Ca2+-activated tension and Ca2+ desensitization of the myofilaments accounted for this contractile dysfunction. The decrease in maximum tension was paralleled by an equivalent decrease in maximum Ca2+-activated myofibrillar ATPase activity. Exposure to high calcium or isoproterenol recruited a sizable contractile reserve in TG muscles, which was proportionately similar to that in control muscles but scaled downward in amplitude. These results suggest that calcium regulatory pathways and β-adrenergic signal transduction remain intact in isolated trabeculae from stunned TG mice, further recapitulating key features of genuine stunned myocardium.

Original languageEnglish (US)
Pages (from-to)H2623-H2630
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number6 49-6
StatePublished - 2001


  • Calcium ion sensitivity
  • Cardiac excitation-contraction coupling
  • Signal transduction

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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