Developmental change of facilitative glucose transporter expression in rat embryonal and fetal intestine

The developmental expression and localization of facilitative glucose transporter protein (GLUT-1, GLUT-2 and GLUT-5) in rat embryonal and fetal intestine were examined using immunohistochemical methods. The intestines were collected from embryo and fetus (term days, 10 to 20 of gestation), newborn and adult rats (16 weeks after birth). GLUT-1 was expressed abundantly in the gut tube on day 10 of gestation. From day 10 to birth, GLUT-1 was expressed continuously but its expression decreased gradually. In the adult, no GLUT-1 was detected. GLUT-2 was not expressed from day 10 to 14, but began to be expressed in the lumen of the gut tube on day 16, before the intestinal villi were evident. On day 18, when the intestinal villi were developing, GLUT-2 was localized to the basolateral membranes of the enterocytes. A similar pattern of GLUT-2 localization was also observed in newborn and adult rat intestines. The expression kinetics of GLUT-5 were almost the same as those of GLUT-2. GLUT-5 began to be expressed in the lumen of the gut tube on day 16. In contrast to GLUT-2, GLUT-5 was localized to the brush border membranes of intestinal villi after day 18. These results indicate that the expression and localization of each member of the glucose transporter family in the embryonal and fetal intestine vary with the gestational phase. GLUT-1 may be required for glucose metabolism early in gestation, and GLUT-2 and GLUT-5 may be required in both late gestational and perinatal stages.