Quantification of subcellular glycogen in resting human muscle: granule size, number, and location.
A few qualitative investigations suggested that location of muscle glycogen (G) granules in specific sites may be associated with distinct metabolic roles. Similarly, it has been suggested that the acid-soluble and -insoluble G fractions (macro- and proglycogen, respectively) are different metabolic pools and also could exist as separate entities. We employed a transmission electron microscopic technique to quantify subcellular G particle size, number, and location in human vastus lateralis biopsies of 11 resting men. The intra- and interobserver variability for the various measures was generally <4%. Granule size and number were quantified in subcellular compartments (subsarcolemmal, intra- and intermyofibrillar). Subcellular location was critical: G was more densely concentrated in the subsarcolemmal than in the myofibrillar space, whereas the single-particle volume was greater in the latter. Single-particle diameter ranged from 10 to 44 etam and followed a continuous, normal distribution. This implies that proglycogen is not a distinct entity, but rather that pro- and macroglycogen are divisions of smaller and larger molecules. These results demonstrate a compartmentalized pattern of subcellular G deposition in human skeletal muscle for both the size and density of granules.
Marchand
I
I
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, N1G 2W1, Ontario, Canada.
Chorneyko
K
K
Tarnopolsky
M
M
Hamilton
S
S
Shearer
J
J
Potvin
J
J
Graham
T E
TE
D000328:Adult; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D008854:Microscopy, Electron / Q000379:methods; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism / Q000648:ultrastructure; D012146:Rest / Q000502:physiology*; D012508:Sarcolemma / Q000378:metabolism / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000378:metabolism*; D014018:Tissue Distribution
D006003:Glycogen