Figure 1. Excision of jejunum results in rapid loss of GLUT2 from the brush-border membrane.

Three pairs of normal jejuna were each perfused with 5 mm fructose in vivo for 30 min and then for different times in vitro; pair 1 was not perfused further (0 min in vitro), pair 2 was perfused for 25 min in vitro and pair 3 was perfused for 60 min in vitro. Three pairs were perfused in the absence of PMA (no PMA, left-hand side) and three pairs in the presence of PMA (with PMA, right-hand side). After perfusion, trafficking was stopped by flushing with ice-cold perfusate, and brush-border membrane vesicles were prepared and blotted for GLUT2. As soon as jejunum from normal rats is excised, PKC is inactivated because of the loss of influence of endogenous hormones, and about 75 % of the GLUT2 is lost from the membrane within minutes. If, however, PKC remains active because the jejunum is perfused with PMA, then GLUT2 is not lost. All types of in vitro preparations from normal, untreated jejunum suffer loss of GLUT2 from the brush-border membrane and the passive component is not readily detectable; see text. Reproduced with permission from Helliwell et al. (2000a), Biochemical Journal 350, 149-154. © The Biochemical Society.