Glucose uptake into Xenopus laevis oocytes expressing wild-type or mutant glut1. Oocytes were injected with 20 ng of WT or mutant glut1 (or 10 ng of WT and 10 ng of mutant where coexpressed). Oocytes expressing WT or mutant glut1 were assayed 2 days after injection (data are means ± SEMs of 4 replicates of 5 oocytes; n = 4). *P < .05, **P < .01, and ***P < .001. (A) Deoxy-D-glucose uptake in Xenopus laevis oocytes. Inset: continuing the same experiment with oocytes assayed 3 days after injection (data are means ± SEMs of 4 replicates of 5 oocytes; n = 4). (B) Inhibition of deoxy-D-glucose uptake in Xenopus laevis oocytes. Oocytes were incubated in MBS or MBS containing phloretin (100μM) and cytochalasin B (50μM) for 20 minutes at room temperature before adding [³H]-deoxy-D-glucose (data are means ± SEMs of 4 replicates of 5 oocytes; n = 4).