Contraction-induced translocation of the glucose transporter Glut4 in isolated ventricular cardiomyocytes.

Field stimulation of isolated adult ventricular cardiomyocytes was used to study the effect of contractile activity on 3-O-methylglucose transport and the subcellular distribution of Glut4. Cells contracting at a frequency of 1 Hz for 30 min exhibited unaltered basal and insulin-stimulated rates of glucose transport when compared to resting cells. However, at 5 Hz 3-O-methylglucose transport increased to 224% of control after 5 min. Under these conditions insulin was unable to produce a significant additional stimulation of glucose transport. Immunoblotting with an anti-Glut4 polyclonal antibody showed that both insulin and contraction (5 Hz) increased the amount of Glut4 in a plasma membrane fraction by about 8-fold with a parallel decrease in an intracellular membrane fraction by 60-65%. These data suggest the existence of an identical insulin- and contraction-recruitable Glut4 transporter pool in cardiomyocytes.