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This Article Full Text Full Text (PDF) All Versions of this Article: 580/2/617    most recent jphysiol.2006.122457v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Marchand, I. Articles by Graham, T. E. Search for Related Content PubMed PubMed Citation Articles by Marchand, I. Articles by Graham, T. E. Related Collections Skeletal Muscle and Exercise

¹ CLSC Faubourg, 2260 Parthenais, Montréal,Québec, Canada H2K 3T5
² Department of Neurology, McMaster University Hamilton, Ontario, Canada L8N 3Z5
³ Childhood Obesity Research Unit, Children's Hospital Eastern Ont, Ottawa, Ontario, Canada K1H 8L1
⁴ Department of Pathology and Molecular Medicine, McMaster University,Hamilton, Ontario, Canada L8N 3Z5
⁵ Department of Pathology, St. Joseph's Healthcare, Hamilton, Ontario, Canada L8N 4A6
⁶ Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1

Although data relating to muscle glycogen are interpreted as showing it is homogenous when quantified biochemically, it is actually in granules in specific subcellular locations. We hypothesized that postexercise restoration of muscle glycogen would occur initially by an increase in granule number followed by an increase in size, and also that restoration would differ in various subcellular locations. Five men performed prolonged exercise and had muscle biopsies taken at 0, 4, 24 and 48 h of recovery. We quantified granule number and size as well as the total volume of glycogen in the subsarcolemmal and the intra- and intermyofibrillar regions, using transmission electron microscopy. Muscle glycogen was reduced to 36 ± 8.3 mmol glucosyl units (kg dry weight)^–1 at exhaustion, and was preferentially depleted and subsequently repleted in the intramyofibrillar space. The repletion rate was greatest in the first 4 h; this was associated with a 186% increase in number (P 0.05) and no change in particle size (P 0.05). From 4 h to 48 h, there was an increase in particle size (P 0.05) but not number (P 0.05). Net rate of G volume synthesis per unit area was 50% greater (P 0.05) in the subsarcolemmal than the myofibrillar compartment. Conversely, the net rate of single-particle volume synthesis was greater (P 0.05) in the myofibrillar than the subsarcolemmal compartment. Glycogen granules varied in size and number depending on location, and in all compartments resynthesis of glycogen was characterized initially by an increase in granule number and later by an increase in size.

(Received 6 October 2006; accepted after revision 26 January 2007; first published online 1 February 2007)
Corresponding author T. Graham: Dept. of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.  Email: terrygra{at}uoguelph.ca

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