Sarcolemmal glucose transport and glut4 translocation during exercise are diminished by endurance training. Richter, Erik A., Palle Jensen, Bente Kiens, and S[stod]oren Kristiansen. Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, 13 Universitetsparken, DK-2100 Copenhagen, Denmark
APStracts 4:0221E, 1997.
Glucose utilization during exercise of a given submaximal power output is decreased after endurance training. The aim of the present study was to elucidate the mechanisms behind this phenomenon utilizing the sarcolemmal giant vesicle technique. 8 healthy young untrained men endurance trained one thigh for three weeks. They then exercised both thighs simultaneously at the same work load (77% of peak oxygen uptake of the untrained thigh) for 40 min. Training increased muscle GLUT4 protein by 70 % (p<0.05). Glucose uptake during exercise was 38 % lower (p<0.05) in the trained (T) thigh than in the untrained (UT) thigh due to both a lower (p<0.05) glucose extraction and blood flow in T. During exercise sarcolemmal GLUT4 protein content and glucose transport capacity increased significantly less in T- than in UT-muscle, and muscle glucose concentration was lower in T compared with UT (p<0.05) at the end of exercise. It is concluded that in spite of a large increase in muscle GLUT4 with endurance training, exercise of a given submaximal power output increases muscle glucose uptake less in trained compared with untrained muscle. It is suggested that the mechanism behind this phenomenon is blunted exercise-induced translocation of GLUT4 to the sarcolemma resulting in a blunted increase in sarcolemmal glucose transport in trained muscle. 

Received 29 May 1997; accepted in final form 1 October 1997.
APS Manuscript Number E248-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997