Please use this identifier to cite or link to this item:
Title: Intracellular glucose and binding of hexokinase and phosphofructokinase to particulate fractions increase under hypoxia in heart of the amazonian armored catfish (Liposarcus pardalis)
Authors: Treberg, Jason R.
MacCormack, Tyson James
Lewis, Johanne Mari
Val, Vera Maria Fonseca Almeida e
Val, Adalberto Luis
Driedzic, William Robert
Keywords: 6 Phosphofructokinase
Citrate Synthase
Fructose-bisphosphate Aldolase
Lactate Dehydrogenase
Lactic Acid
Pyruvate Kinase
6 Phosphofructokinase
Cardiovascular System
Comparative Study
Enzyme Activity
Particulate Matter
Cell Hypoxia
Heart Contraction
Heart Mitochondrion
Heart Muscle
Heart Ventricle
Heart Ventricle Function
In Vitro Study
Cell Hypoxia
Citrate (si)-synthase
Fructose-bisphosphate Aldolase
Heart Ventricles
L-lactate Dehydrogenase
Lactic Acid
Mitochondria, Heart
Myocardial Contraction
Pyruvate Kinase
Ventricular Function
Amazon Basin
South America
Liposarcus Pardalis
Issue Date: 2007
metadata.dc.publisher.journal: Physiological and Biochemical Zoology
metadata.dc.relation.ispartof: Volume 80, Número 5, Pags. 542-550
Abstract: Armored catfish (Liposarcus pardalis), indigenous to the Amazon basin, have hearts that are extremely tolerant of oxygen limitation. Here we test the hypothesis that resistance to hypoxia is associated with increases in binding of selected glycolytic enzymes to subcellular fractions. Preparations of isolated ventricular sheets were subjected to 2 h of either oxygenated or hypoxic (via nitrogen gassing) treatment during which time the muscle was stimulated to contract. The bathing medium contained 5 mM glucose and was maintained at 25°C. Initial experiments revealed increases in anaerobic metabolism, There was no measurable decrease in glycogen level; however, hypoxic treatment led to a twofold increase in heart glucose and a 10-fold increase in lactate content. It is suggested that the increase in heart glucose content is a result of an enhanced rate of facilitated glucose transport that exceeds the rate of phosphorylation of glucose. Further experiments assessed activities of metabolic enzymes in crude homogenates and subsequently tracked the degree of enzyme binding associated with subcellular fractions. Total maximal activities of glycolytic enzymes (hexokinase [HK], phosphofructokinase [PFK], aldolase, pyruvate kinase, lactate dehydrogenase), and a mitochondrial marker, citrate synthase, were not altered with the hypoxic treatment. A substantial portion (≥50%) of HK is permanently bound to mitochondria, and this level increases under hypoxia. The amount of HK that is bound to the mitochondrial fraction is at least fourfold higher in hearts of L. pardalis than in rat hearts. Hypoxia also resulted in increased binding of PFK to a particulate fraction, and the degree of binding is higher in hypoxia-tolerant fish than in hypoxia-sensitive mammalian hearts. Such binding may be associated with increased glycolytic flux rates through modulation of enzyme-specific kinetics. The binding of HK and PFK occurs before any significant decrease in glycogen level. © 2007 by The University of Chicago. All rights reserved.
metadata.dc.identifier.doi: 10.1086/520129
Appears in Collections:Artigos

Files in This Item:
There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.