Altered subcellular Ca2+ regulation in papillary muscles from cardiomyopathic hamster hearts

E. Keller, C. S. Moravec, M. Bond

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14 Citations (Scopus)


To investigate whether cardiac dysfunction in prefailure cardiomyopathic (CM) hamster hearts is due to Ca2+ overload or alternatively to decreased availability of Ca2+ in the sarcoplasmic reticulum (SR), the Ca2+ channel agonist, BAY K 8644, was used to compare the effects of increased Ca2+ influx on function and subcellular Ca2+ distribution in papillary muscles from hearts of 110-day-old CM and normal hamsters. A band, mitochondrial, and junctional SR Ca2+ were measured by electron probe microanalysis in CM and normal papillary muscles, which were either untreated or pretreated with BAY K 8644. Muscles were then rapidly frozen during contraction or relaxation. The results showed decreased tension development and decreased inotropic response to BAY K 8644 in CM muscles versus normals. There was no elevation of mitochondrial or A-band Ca2+ in BAY K 8644-treated or untreated CM muscles frozen during contraction or relaxation compared with similarly treated normals. In muscles frozen during relaxation, junctional SR Ca2+ was lower in both untreated and BAY K 8644-treated CM muscles versus comparably treated normals. These results do not support the hypothesis of an increased sensitivity to Ca2+ in hypertrophied, prefailure CM hearts but do indicate that less Ca2+ is available in the SR for activation of contraction.

Original languageEnglish
Pages (from-to)H1875-H1883
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number5 37-5
Publication statusPublished - 1995


  • BAY K 8644
  • electron probe microanalysis
  • sarcoplasmic reticulum

ASJC Scopus subject areas

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

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