Figure 1.

Insulin responsiveness of both 2-deoxyglucose uptake and cell surface transferrin binding by 3T3-L1 cells increases dramatically between days 2 and 3 of differentiation. On the indicated days after the induction of differentiation, cells were serum starved for 2 h before treatment with (black bars) or without (striped bars) 100 nM insulin for 15 min at 37°C. ³H-2-deoxyglucose (2-DOG) uptake (A) and cell surface ¹²⁵I-transferrin (Tf) binding (C) were then determined as described in MATERIALS AND METHODS. Each bar and error bar represent the average and difference between duplicate determinations, respectively. The fold stimulation of 2-deoxyglucose uptake (B) and transferrin binding (D) was then calculated by dividing the average of the insulin-stimulated condition by that of the basal for each time point. These data are representative of three independent experiments.