Immunohistochemical localization of facilitated-diffusion glucose transporters in rat pancreatic islets.
The subcellular localization of five isoforms of facilitated-diffusion glucose transporters (GLUTs), from GLUT1 to GLUT5, in rat pancreatic islets was studied by immunohistochemistry using rabbit polyclonal antisera against mouse or rat GLUT peptides. Animals were perfusion-fixed with phosphate-buffered 4% paraformaldehyde and the pancreases were removed. Some specimens were embedded in paraffin, serially sectioned, and immunostained for glucagon, insulin, somatostatin, and the GLUTs for light microscopic observation. Others were prepared for immunoelectron microscopy by the post-embedding method. By these methods, GLUT2 immunostaining was observed on the lateral membranes of pancreatic beta-cells, whereas GLUT3 immunoreaction was predominantly localized in the cytoplasm of beta-cells and was not found in alpha-cells. In contrast, GLUT5 immunostaining was preferentially localized in the cytoplasm of alpha-cells compared to that of beta-cells. However, GLUT1 and GLUT4 were either barely or not at all detectable in any cells. These results suggest that rat islets take up glucose by at least three different processes and that blood glucose levels could be modulated differentially by: a high Km glucose transporter, GLUT2, in beta-cells; by a low Km glucose transporter, GLUT3, in beta-cells; and by a low Km glucose transporter, GLUT5, in alpha-cells.
Sato
Y
Y
Department of Pathology, Yokohama City University School of Medicine, Japan.
Ito
T
T
Udaka
N
N
Kanisawa
M
M
Noguchi
Y
Y
Cushman
S W
SW
Satoh
S
S
D000595:Amino Acid Sequence; D000818:Animals; D005934:Glucagon / Q000032:analysis; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D051296:Glucose Transporter Type 5; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis; D007515:Islets of Langerhans / Q000737:chemistry* / Q000648:ultrastructure; D008297:Male; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D013047:Specific Pathogen-Free Organisms
D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D051296:Glucose Transporter Type 5; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; C495679:Slc2a1 protein, rat; C495690:Slc2a3 protein, rat; C495694:Slc2a4 protein, rat; D005934:Glucagon