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Adaptive responses of GLUT-4 and citrate synthase in fast-twitch muscle of voluntary running ratsGlucose transporter (GLUT-4) protein, hexokinase, and citrate synthase (proteins involved in oxidative energy production from blood glucose catabolism) increase in response to chronically elevated neuromuscular activity. It is currently unclear whether these proteins increase in a coordinated manner in response to this stimulus. Therefore, voluntary wheel running (WR) was used to chronically overload the fast-twitch rat plantaris muscle and the myocardium, and the early time courses of adaptative responses of GLUT-4 protein and the activities of hexokinase and citrate synthase were characterized and compared. Plantaris hexokinase activity increased 51% after just 1 wk of WR, whereas GLUT-4 and citrate synthase were increased by 51 and 40%, respectively, only after 2 wk of WR. All three variables remained comparably elevated (+50-64%) through 4 wk of WR. Despite the overload of the myocardium with this protocol, no substantial elevations in these variables were observed. These findings are consistent with a coordinated upregulation of GLUT-4 and citrate synthase in the fast-twitch plantaris, but not in the myocardium, in response to this increased neuromuscular activity. Regulation of hexokinase in fast-twitch muscle appears to be uncoupled from regulation of GLUT-4 and citrate synthase, as increases in the former are detectable well before increases in the latter.
Document ID
20050000262
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Henriksen, E. J.
(University of Arizona Tucson 85721)
Halseth, A. E.
Date Acquired
August 22, 2013
Publication Date
January 1, 1995
Publication Information
Publication: The American journal of physiology
Volume: 268
Issue: 1 Pt 2
ISSN: 0002-9513
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Number 40-40
NASA Program Space Biology
NASA Discipline Musculoskeletal

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