Pflügers Archiv

, Volume 442, Issue 1, pp 101–106

Increased muscle glycogen content is associated with increased capacity to respond to T-system depolarisation in mechanically skinned skeletal muscle fibres from the rat

  • Melissa Barnes
  • L.M. Gibson
  • D. George Stephenson
Original Article

DOI: 10.1007/s004240000510

Cite this article as:
Barnes, M., Gibson, L. & Stephenson, D. Pflügers Arch - Eur J Physiol (2001) 442: 101. doi:10.1007/s004240000510

Abstract

The ability of mechanically skinned muscle fibres from the rat to respond to T-system depolarisation was studied in relation to muscle glycogen content. Muscle glycogen was altered by incubating extensor digitorum longus (EDL) muscles in Krebs solution without glucose or in Krebs solution with glucose (10 mM) and insulin (20 U·l–1). The glycogen content of muscles stored without glucose was rather stable between 30 and 480 min (11.27±0.39 µmol·g–1), while the muscles stored with glucose and insulin maintained an elevated and stable level of glycogen (23.48±1.67 µmol·g–1) between 100 and 360 min. Single mechanically skinned fibres from paired muscles, incubated in either glucose-free Krebs or in Krebs with glucose and insulin, were subjected to cycles of T-system depolarisation–repolarisation in a controlled environment (8 mM ATP, 10 mM creatine phosphate, 1 mM Mg2+, pH 7.10) and the force response was monitored until the force had declined to 50% of the maximum response (50% rundown). Fibres from muscles with a higher glycogen content reached 50% rundown after a larger number of depolarisations and displayed consistently larger average response capacity values, calculated as the sum of the force responses to 50% rundown divided by the maximum Ca2+-activated force response in that fibre. Thus skinned fibres originating from muscles with a higher glycogen content have an increased ability to respond to T-system depolarisation when the effect of metabolite accumulation is minimised and the function of glycogen acting as an energy source is by-passed. This provides direct support to the hypothesis that glycogen has a protective role in maintaining fibre excitability.

Fatigue Glycogen Mammalian muscle Skeletal muscle Skinned fibre 

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Melissa Barnes
    • 1
  • L.M. Gibson
    • 2
  • D. George Stephenson
    • 1
  1. 1.Department of Zoology, La Trobe University, Bundoora, Victoria 3086Australia
  2. 2.Department of Biological Sciences, Technology and Environment, La Trobe University, Bendigo 3550Australia