REGULATION OF GLUCOSE-TRANSPORT, AND GLUCOSE TRANSPORTERS EXPRESSION AND TRAFFICKING IN THE HEART - STUDIES IN CARDIAC MYOCYTES

Cardiac muscle is characterized by a high rate of glucose consumption. In the absence of insulin, glucose transport into cardiomyocytes limi ts the rate of glucose utilization and therefore it is important to un derstand the regulation of glucose transporters, Cardiac muscle cells express 2 distinct glucose transporters, GLUT4 and GLUT1; although GLU T4 is quantitatively the more important glucose transporter expressed in heart, GLUT1 is also expressed at a substantial level, In isolated rat cardiomyocytes, insulin acutely stimulates glucose transport and t ranslocates both GLUT4 and GLUT1 from an intracellular site to the cel l surface, Recent evidence indicates the existence of at least 2 disti nct intracellular membrane populations enriched in GLUT4 with a differ ent protein composition, Elucidation of the intracellular location of these 2 GLUT4 vesicle pools in cardiac myocytes, their role in GLUT4 t rafficking, and their relation to insulin-induced GLUT4 translocation needs to be addressed. (C) 1997 by Excerpta Medica, Inc.