Spark- and ember-like elementary Ca2+ release events in skinned fibres of adult mammalian skeletal muscle

Authors

  • Wolfgang G. Kirsch,

    1. Institute of Physiology and Pathophysiology, Medical Biophysics, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
    Search for more papers by this author
  • Dietmar Uttenweiler,

    1. Institute of Physiology and Pathophysiology, Medical Biophysics, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
    Search for more papers by this author
  • Rainer H. A. Fink

    Corresponding author
    1. Institute of Physiology and Pathophysiology, Medical Biophysics, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
    • Corresponding author
      R. H. A. Fink: Institute of Physiology and Pathophysiology, Medical Biophysics, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany., Email: rainer.fink@urz.uni-heidelberg.de

    Search for more papers by this author

Abstract

  • 1Using laser scanning confocal microscopy, we show for the first time elementary Ca2+ release events (ECRE) from the sarcoplasmic reticulum in chemically and mechanically skinned fibres from adult mammalian muscle and compare them with ECRE from amphibian skinned fibres.
  • 2Hundreds of spontaneously occurring events could be measured from individual single skinned mammalian fibres. In addition to spark-like events, we found ember-like events, i.e. long-lasting events of steady amplitude. These two different fundamental release types in mammalian muscle could occur in combination at the same location.
  • 3The two peaks of the frequency of occurrence for ECRE of mammalian skeletal muscle coincided with the expected locations of the transverse tubular system within the sarcomere, suggesting that ECRE mainly originate at triadic junctions.
  • 4ECRE in adult mammalian muscle could also be identified at the onset of the global Ca2+ release evoked by membrane depolarisation in mechanically skinned fibres. In addition, the frequency of ECRE was significantly increased by application of 0.5 mm caffeine and reduced by application of 2 mm tetracaine.
  • 5We conclude that the excitation-contraction coupling process in adult mammalian muscle involves the activation of both spark- and ember-like elementary Ca2+ release events.

Ancillary