Affiliation:
1. the Department of Internal Medicine, Yale University School of Medicine, New Haven; the Department of Physiology, Yale University School of Medicine (M.C.), New Haven; and Bayer Metabolic Disorders Research Division (J.R.), West Haven, Conn.
Abstract
Background
Myocardial ischemia increases heart glucose utilization in vivo. However, whether low-flow ischemia leads to the translocation of glucose transporter (GLUT)-4 and/or GLUT-1 to the sarcolemma in vivo is unknown.
Methods and Results
In a canine model, we evaluated myocardial glucose metabolism in vivo and the distribution of GLUT-4 and GLUT-1 by use of immunoblotting of sarcolemma and intracellular membranes and immunofluorescence localization with confocal microscopy. In vivo glucose extraction increased fivefold (
P
<.001) and was associated with net lactate release in the ischemic region. Ischemia led to an increase in the sarcolemma content of both GLUT-4 (15±2% to 30±3%,
P
<.02) and GLUT-1 (41±4% to 58±3%,
P
<.03) compared with the nonischemic region and to a parallel decrease in their intracellular contents. Immunofluorescence demonstrated the presence of both GLUT-4 and GLUT-1 on cardiac myocytes. GLUT-1 had a more prominent cell surface pattern than GLUT-4, which was primarily intracellular in the nonischemic region. However, significant GLUT-4 surface labeling was found in the ischemic region.
Conclusions
Translocation of the insulin-responsive GLUT-4 transporter from an intracellular storage pool to the sarcolemma occurs in vivo during acute low-flow ischemia. GLUT-1 is also present in an intracellular storage pool from which it undergoes translocation to the sarcolemma in response to ischemia. These results indicate that both GLUT-1 and GLUT-4 are important in ischemia-mediated myocardial glucose uptake in vivo.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Cited by
142 articles.
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