Exercise induces recruitment of the "insulin-responsive glucose transporter". Evidence for distinct intracellular insulin- and exercise-recruitable transporter pools in skeletal muscle.
Acute exercise, like insulin, increases D-glucose uptake into rat hind limb muscles. Here we examine the distribution of the muscle glucose transporters GLUT-4 and GLUT-1 in plasma membrane and intracellular membrane fractions of skeletal muscle prepared from control, exercised, and acutely insulin-treated rats. Immunoblotting with an anti-GLUT-4 polyclonal antibody showed that acute insulin treatment (by hind limb perfusion or in vivo injection) increased GLUT-4 transporters in a plasma membrane fraction and decreased them in an intracellular membrane fraction. Exercise also increased the GLUT-4 transporters in the plasma membrane, but in contrast to insulin, did not significantly decrease them in the intracellular fraction. Immunoblotting with anti-GLUT-1 antibody revealed that this transporter is largely localized in the plasma membrane. Neither insulin nor exercise significantly increased GLUT-1 transporters in the plasma membrane. The data show that GLUT-4 is an insulin-responsive glucose transporter in skeletal muscle and, furthermore, that GLUT-4 also responds to acute exercise. The results are consistent with recruitment of GLUT-4 glucose transporters to the plasma membrane from intracellular stores. Moreover, exercise-sensitive GLUT-4 transporters do not originate from the insulin-sensitive intracellular membrane fraction, suggesting the existence of distinct intracellular insulin- and exercise-recruitable GLUT-4 transporter pools.
Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
A G
AG
Douen
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T
Ramlal
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S
Rastogi
P J
PJ
Bilan
G D
GD
Cartee
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Vranic
J O
JO
Holloszy
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Klip
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003571:Cytochalasin B / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism / Q000502:physiology*; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D007328:Insulin; D009004:Monosaccharide Transport Proteins; D003571:Cytochalasin B; D005947:Glucose