Insulin recruits GLUT4 mainly from a
CD-MPR-negative GLUT4-vesicle pool, but also from CD-MPR-positive
vesicles. Preparation, as shown in Figure 4D, was quantified similar to
that shown in Figure 6. Compared with basal adipocytes (A) and after
insulin stimulation (B), a clear change in the distribution of vesicles
is visible. The average number of GLUT4 gold particles in
CD-MPR-positive vesicles decreased upon insulin stimulation (C), and
GLUT4 disappeared from the CD-MPR-negative vesicle pool (D). The number
of vesicles containing only GLUT4 and no CD-MPR decreased upon insulin
treatment (E, p < 0.005). Insulin caused a decrease of the ratio
of GLUT4-gold particles over CD-MPR-gold particles in
GLUT4-positive/CD-MPR-positive vesicles (F, p < 0.01).