title: High rates of glucose utilization in the gas gland of Atlantic cod (Gadus morhua) are supported by GLUT1 and HK1b.
abstract: The gas gland of physoclistous fish utilizes glucose to generate lactic acid that leads to the off-loading of oxygen from haemoglobin. This study addresses characteristics of the first two steps in glucose utilization in the gas gland of Atlantic cod (Gadus morhua). Glucose metabolism by isolated gas gland cells was 12- and 170-fold higher, respectively, than that in heart and red blood cells (RBCs) as determined by the production of (3)H2O from [2-(3)H]glucose. In the gas gland, essentially all of the glucose consumed was converted to lactate. Glucose uptake in the gas gland shows a very high dependence upon facilitated transport as evidenced by saturation of uptake of 2-deoxyglucose at a low extracellular concentration and a requirement for high levels of cytochalasin B for uptake inhibition despite the high efficacy of this treatment in heart and RBCs. Glucose transport is via glucose transporter 1 (GLUT1), which is localized to the glandular cells. GLUT1 western blot analysis from whole-tissue lysates displayed a band with a relative molecular mass of 52 kDa, consistent with the deduced amino acid sequence. Levels of 52 kDa GLUT1 in the gas gland were 2.3- and 33-fold higher, respectively, than those in heart and RBCs, respectively. Glucose phosphorylation is catalysed by hexokinase Ib (HKIb), a paralogue that cannot bind to the outer mitochondrial membrane. Transcript levels of HKIb in the gas gland were 52- and 57-fold more abundant, respectively, than those in heart and RBCs. It appears that high levels of GLUT1 protein and an unusual isoform of HKI are both critical for the high rates of glycolysis in gas gland cells.
authors.affiliation: Department of Ocean Sciences, Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7.
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Clow
authors.affiliation: Department of Ocean Sciences, Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7.
authors.forename: Connie E
authors.initials: CE
authors.lastname: Short
authors.affiliation: Aquatic Research Cluster, CREAIT Network, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Hall
authors.affiliation: Division of BioMedical Sciences, Faculty of Medicine, Memorial University, St John's, NL, Canada A1B 3V6.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Gendron
authors.affiliation: Division of BioMedical Sciences, Faculty of Medicine, Memorial University, St John's, NL, Canada A1B 3V6.
authors.forename: Hélène
authors.initials: H
authors.lastname: Paradis
authors.affiliation: Division of BioMedical Sciences, Faculty of Medicine, Memorial University, St John's, NL, Canada A1B 3V6.
authors.forename: Ankur
authors.initials: A
authors.lastname: Ralhan
authors.affiliation: Department of Ocean Sciences, Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7 wdriedzic@mun.ca.
authors.forename: William R
authors.identifier: 0000-0002-4105-1766
authors.initials: WR
authors.lastname: Driedzic
mesh_terms: D000825:Animal Structures / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002469:Cell Separation; D003571:Cytochalasin B / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D048389:Gadus morhua / Q000033:anatomy & histology* / Q000378:metabolism*; D005740:Gases / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism*; D007150:Immunohistochemistry; D019344:Lactic Acid / Q000378:metabolism; D008970:Molecular Weight; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D005740:Gases; D051272:Glucose Transporter Type 1; D012333:RNA, Messenger; D019344:Lactic Acid; D003571:Cytochalasin B; D003847:Deoxyglucose; D006593:Hexokinase; D005947:Glucose
keywords: Facilitated transport; Glucose metabolism; Heart; RBC; [2-3H]glucose