title: The glucose transporter in the plasma membrane of the outer segments of bovine retinal rods.
abstract: The facilitated diffusion glucose transporter in the plasma membrane of intact outer segments isolated from bovine retinal rods (ROS) was characterized by measurements of: (1) 14C-labeled 3-O-methylglucose fluxes; and (2) glucose-sensitive binding of 3H-labeled cytochalasin B to ROS membranes. Inhibition of 3-O-methylglucose influx into ROS, inhibition of 3-O-methylglucose efflux from ROS and glucose-sensitive binding of cytochalasin B to ROS showed very similar cytochalasin B inhibition/dissociation constants of 0.9 microM, 1.3 microM and 1.3 microM, respectively. D-glucose inhibited both 14C-labeled 3-O-methylglucose transport and cytochalasin B binding. The above results suggest that D-glucose-sensitive cytochalasin B binding reflects specific binding to the ROS glucose transporter and the density of glucose transporter in the ROS plasma membrane was determined to be 800 microns-2, comparable to relatively abundant ROS plasma membrane proteins such as the cGMP-gated channel and the Na-Ca+K exchanger. Displacement of 3H-labeled cytochalasin B by non-transportable hexoses was used to localize the hexose transporters to the ROS plasma membrane and to examine a simple single-site, alternating conformation model for hexose transport. A comparison between the Glut1 glucose transporters of bovine ROS, bovine erythrocytes and human erythrocytes suggests that kinetic and pharmacological characteristics of glucose transporters cannot be predicted in a simple manner from gene type and species.
authors: Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
authors: X B
authors: XB
authors: Li
authors: R T
authors: RT
authors: Szerencsei
authors: P P
authors: PP
authors: Schnetkamp
mesh_terms: D019325:3-O-Methylglucose; D000818:Animals; D001665:Binding Sites; D001786:Blood Glucose / Q000378:metabolism; D002417:Cattle; D003571:Cytochalasin B / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism; D066298:In Vitro Techniques; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose; D003571:Cytochalasin B