Insulin stimulates GLUT4 translocation toward the cell surface and increases glucose uptake into 3T3-L1-GLUT4myc adipocytes. (A) Cells were left untreated or treated with insulin at the concentrations indicated for 20 min. Then, cells were lysed and separated into the cytosolic (C) and plasma membrane fractions (M), followed by western blotting using antibody against c-myc. In the graph, each column represents the mean (±s.e.m.) ratio of signal intensity for c-myc in the plasma membrane fraction to that in the total cell (n=4 independent experiments). (B) Cells were incubated in PBS containing glucose (10 mM) for periods of time as indicated in the presence and absence of insulin (100 nM), and then extracellular glucose was measured by HPLC. In the graph, each column represents the mean (±s.e.m.) glucose uptake (nmol/μg protein per min) (n=4 independent experiments). P values, unpaired t-test.