STRUCTURAL-FUNCTIONAL ANALYSIS OF THE ROLE PLAYED BY FACILITATED DIFFUSION IN THE PROCESS OF GLUCOSE
ABSORPTION BY RAT SMALL INTESTINE ENTEROCYTES
N. M. Grefner,1 L. V. Gromova,2 A. A. Gruzdkov,2
E. S. Snigirevskaya,1 Ya. Yu. Komissarchik 1
1 Institute of Cytology RAS and 2 Pavlov Institute of Physiology RAS, St. Petersburg;
e-mail: yykomis@mail.cytspb.rssi.ru
To elucidate mechanisms providing transport of sugars across intestinal epithelium, on taking into account the
current hypotheses (active transport, participation of paracellular transport and passive component of transcellular
transport), it was important to reveal structural changes of tight junctions and distribution of the carriers of
facilitated diffusion of GLUT2 and protein kinase C during absorption of glucose. On using confocal and electron
microscopy, ultrastructural and immunocytochemical studies of enterocytes after perfusion of isolated rat small
intestine fragment with 75 mM glucose (chronic experiment) have shown: 1) fluorescent labels of transporter GLUT2
and PKCaII are located in the apical area of enterocytes situated at the upper half of the villus. Antibodies
against GLUT2, conjugated with gold, are revealed at the microvilli or apical membrane and in the area of terminal
network; 2) no ultrastructural changes of the tight junction are detected on ultrathin sections and freeze-fracture
replics. At the same time, fluorescent and gold labels against actin are concentrated in the vicinity of the
lateral membrane in the tight junction area. The results obtained can serve a confirmation of a hypothesis that at
high glucose concentrations GLUT2 participates in its transfer across the apical membrane.
Key words: confocal and electron microscopy, transepithelial transport, glucose, GLUT2, SGLT1, PKC
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