Topographical localization of muscle glycogen: an ultrahistochemical study in the human vastus lateralis.
The fine structural pattern of glycogen storage in resting and sprint-exercised human vastus lateralis muscle fibres of different types was analysed using ultrahistochemical methods. Three male subjects (31-36 years) performed 60 consecutive, supramaximal bouts of bicycle exercise, each starting every 1 min and having a duration of 8 s (including approximately 3 s of acceleration). The load was estimated to correspond to 200% of VO2-max. Five other subjects (22-27 years) constituted controls. Ultrathin sections stained with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) clearly revealed a compartmental distribution of glycogen. Glycogen is stored at five topographically, and probably also functionally, different locations. They are the subsarcolemmal, intermyofibrillar, para-Z-disc, N2-line, and H-zone spaces. During the exercise, glycogen from the N2-line and para-Z-disc locations is preferentially utilized. Serial sections stained with uranyl acetate and lead citrate demonstrated that glycogen stores of the type 2 fibres were more depleted than those of type 1 fibres. The implications of the differential intracellular glycogen storage are discussed.
Fridén
J
J
Departments of Anatomy, University of Umeå, Sweden.
Seger
J
J
Ekblom
B
B
D000328:Adult; D015444:Exercise; D006003:Glycogen / Q000378:metabolism*; D006651:Histocytochemistry; D006801:Humans; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism* / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism; D013194:Staining and Labeling
D006003:Glycogen