Regulation of cell surface GLUT1, GLUT3, and GLUT4 by insulin and IGF-I in L6 myotubes.

The effects of insulin and IGF-I on the cell surface quantities of GLUT1, GLUT3 and GLUT4 glucose transporters in L6 myotubes were determined with the exofacial bis-mannose phololabel (ATB-BMPA). In basal cells, an equal molar quantity of each transporter isoform was found at the cell surface. Insulin stimulated the translocation of all three glucose transporter isoforms to the plasma membrane fraction from the light microsome fraction, resulting in equal molar quantities on the cell surface. IGF-I stimulated a similar translocation of all isoforms, augmented by an increase in surface GLUT3 as assessed by ATB-BMPA.