VANADATE INDUCES THE RECRUITMENT OF GLUT-4 GLUCOSE TRANSPORTER TO THE PLASMA-MEMBRANE OF RAT ADIPOCYTES

In rat adipocytes, the insulin stimulation of the rate of glucose uptake is due, at least partially, to the recruitment of glucose transporter proteins from an intracellular compartment to the plasma membrane. Vanadate is a known insulin mimetic agent and causes an increase in the rate of glucose transport in rat adipocytes similar to that seen with insulin. The objective of the present study was to determine whether vanadate exerts its effect through the recruitment of glucose transporters to the plasma membrane. We report that under conditions where vanadate stimulates the rate of 2-deoxyglucose uptake to the same extent as insulin, the concentration of GLUT-4 in the plasma membrane was increased similarly by both insulin and vanadate, and its concentration was decreased in the low density microsomal fraction. These results suggest that vanadate induces the recruitment of GLUT-4 to the plasma membrane. The effects of vanadate and insulin on the stimulation of 2-deoxyglucose uptake and recruitment of GLUT-4 were not additive. This is the first report of an effect of vanadate on the intracellular distribution of the glucose transporter.