Effects of exercise training on glucose transport and cell-surface
glut4 in isolated rat epitrochlearis muscle.
Reynolds, Thomas H., Joseph T. Brozinick, Marc A. Rogers, and Samuel
W. Cushman.
Experimental Diabetes, Metabolism, and Nutrition Section, Diabetes
Branch, NIDDK, National Institutes of Health, Bethesda MD 20892-1420,
Department of Kinesiology, University of Maryland, College Park, MD
20742
APStracts 3:0212E, 1996.
The effects of exercise training on maximal glucose transport activity
and cell-surface GLUT4 was examined in rat epitrochlearis muscle.
Five days of swim training (2 x 3-h ) produces a significant increase
in citrate synthase activity (24.5+0.6 vs. 20.1+0.7 umol/min/g),
GLUT4 content (22.9+0.8 vs. 17.4+0.4 % GLUT4 std), and glycogen
levels (54.3+9.4 vs. 28.6+9.4 umol/g). Maximally insulin-stimulated
glucose transport activity and cell-surface GLUT4 are increased by
55% (1.50+0.11 vs. 0.97+0.10 umol/ml/20 min) and 48% (12.0+0.8 vs.
8.1+0.9 dpm/mg) respectively, in exercise-trained epitrochlearis
muscles. In contrast, hypoxia-stimulated glucose transport activity
and cell-surface GLUT4 are reduced by 38% (0.78+0.08 vs.1.25+0.14
umol/ml/20 min) and 40% (5.7+0.9 vs. 9.4+1.2 dpm/mg), respectively,
in exercise-trained epitrochlearis muscles. These results demonstrate
that changes in insulin- and hypoxia-stimulated glucose transport
activity following exercise training are fully accounted for by the
appearance of cell-surface GLUT4 and support the concept of two
intracellular pools of GLUT4. Finally, we propose that high levels of
muscle glycogen with exercise training may contribute to the decrease
in hypoxia-stimulated glucose transport activity.
Received 6 May 1996; accepted in final form 24 September 1996.
APS Manuscript Number E219-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996