Functional localization of glucose transporter 2 in rat liver

Heterogeneity of zonal hepatocytes is important to elicit specific liver function. We investigated the distribution of glucose transporter 2 (GLUT-2) in normal rat liver by immunostaining and Northern blot analysis. GLUT-2 stained by immunohistochemistry was distributed predominantly in the periportal hepatocytes and gradually thinned towards the perivenous zone. Ultrastructural immunostaining of GLUT-2 showed that it was localized on microvilli of the sinusoidal plasma membrane of hepatocytes but not on the basolateral plasma membrane. Consistent with the distribution of GLUT-2 protein, the level of GLUT-2 mRNA in periportal hepatocytes was 1.9-fold higher than in perivenous hepatocytes selectively isolated by the differential isolation technique. In addition, the mRNA level of phosphoenolpyruvate carboxykinase, one of the key enzymes of gluconeogenesis, was also twofold higher in the periportal hepatocytes. These results suggest that GLUT-2 contributes to the functional difference between periportal and perivenous hepatocytes in glucose metabolism of the liver.