Tubular system volume changes in twitch fibres from toad and rat skeletal muscle assessed by confocal microscopy

Launikonis, Bradley S. and Stephenson, D. George (2002) Tubular system volume changes in twitch fibres from toad and rat skeletal muscle assessed by confocal microscopy. Journal of Physiology, 538 2: 607-618. doi:10.1013/jphysiol.2001.012920


Author Launikonis, Bradley S.
Stephenson, D. George
Title Tubular system volume changes in twitch fibres from toad and rat skeletal muscle assessed by confocal microscopy
Journal name Journal of Physiology   Check publisher's open access policy
ISSN 0022-3751
Publication date 2002-01-01
Sub-type Article (original research)
DOI 10.1013/jphysiol.2001.012920
Volume 538
Issue 2
Start page 607
End page 618
Total pages 12
Place of publication New York
Publisher Blackwell on behalf of Physiological Society
Language eng
Abstract The volume of the extracellular compartment (tubular system) within intact muscle fibres from cane toad and rat was measured under various conditions using confocal microscopy. Under physiological conditions at rest, the fractional volume of the tubular system (t-sys(Vol)) was 1.38 +/- 0.09% (n = 17),1.41 +/- 0.09% (n = 12) and 0.83 +/- 0.07% (n = 12) of the total fibre volume in the twitch fibres from toad iliofibularis muscle, rat extensor digitorum longus muscle and rat soleus muscle, respectively. In toad muscle fibres, the t-sys(Vol) decreased by 30% when the tubular system was fully depolarized and decreased by 15% when membrane cholesterol was depleted from the tubular system with methyl-beta-cyclodextrin but did not change as the sarcomere length was changed from 1.93 to 3.30 mum. There was also an increase by 30% and a decrease by 25% in t-sys(Vol) when toad fibres were equilibrated in solutions that were 2.5-fold hypertonic and 50% hypotonic, respectively. When the changes in total fibre volume were taken into consideration, the t-sys(Vol) expressed as a percentage of the isotonic fibre volume did actually decrease as tonicity increased, revealing that the tubular system in intact fibres cannot be compressed below 0.9% of the isotonic fibre volume. The results can be explained in terms of forces acting at the level of the tubular wall. These observations have important physiological implications showing that the tubular system is a dynamic membrane structure capable of changing its volume in response to the membrane potential, cholesterol depletion and osmotic stress but not when the sarcomere length is changed in resting muscle.
Keyword Physiology
Membrane Capacity
Reversible Vacuolation
Sarcoplasmic-reticulum
Frog-muscle
T-system
Fibers
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biomedical Sciences Publications
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 26 times in Thomson Reuters Web of Science Article | Citations
Google Scholar Search Google Scholar
Created: Mon, 13 Aug 2007, 22:49:57 EST