PMID- 17717817
OWN - NLM
STAT- MEDLINE
DCOM- 20071106
LR  - 20141120
IS  - 1522-2152 (Print)
IS  - 1522-2152 (Linking)
VI  - 80
IP  - 5
DP  - 2007 Sep-Oct
TI  - Intracellular glucose and binding of hexokinase and phosphofructokinase to 
      particulate fractions increase under hypoxia in heart of the amazonian armored 
      catfish (Liposarcus pardalis).
PG  - 542-50
AB  - 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 
      degrees 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.
FAU - Treberg, Jason R
AU  - Treberg JR
AD  - Department of Biochemistry, Ocean Sciences Centre, Memorial University of 
      Newfoundland, St. John's, Newfoundland A1C 5S7, Canada.
FAU - MacCormack, Tyson J
AU  - MacCormack TJ
FAU - Lewis, Johanne M
AU  - Lewis JM
FAU - Almeida-Val, Vera M F
AU  - Almeida-Val VM
FAU - Val, Adalberto L
AU  - Val AL
FAU - Driedzic, William R
AU  - Driedzic WR
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20070713
PL  - United States
TA  - Physiol Biochem Zool
JT  - Physiological and biochemical zoology : PBZ
JID - 100883369
RN  - 33X04XA5AT (Lactic Acid)
RN  - EC 1.1.1.27 (L-Lactate Dehydrogenase)
RN  - EC 2.3.3.1 (Citrate (si)-Synthase)
RN  - EC 2.7.1 - (Phosphofructokinases)
RN  - EC 2.7.1.1 (Hexokinase)
RN  - EC 2.7.1.40 (Pyruvate Kinase)
RN  - EC 4.1.2.13 (Fructose-Bisphosphate Aldolase)
RN  - IY9XDZ35W2 (Glucose)
SB  - IM
MH  - Animals
MH  - Catfishes/*metabolism/physiology
MH  - Cell Hypoxia/physiology
MH  - Citrate (si)-Synthase/metabolism
MH  - Fructose-Bisphosphate Aldolase/metabolism
MH  - Glucose/*metabolism
MH  - Glycolysis
MH  - Heart Ventricles/enzymology/metabolism
MH  - Hexokinase/*metabolism
MH  - In Vitro Techniques
MH  - L-Lactate Dehydrogenase/metabolism
MH  - Lactic Acid/metabolism
MH  - Mitochondria, Heart/enzymology/metabolism
MH  - Myocardial Contraction
MH  - Myocardium/enzymology/*metabolism
MH  - Phosphofructokinases/*metabolism
MH  - Pyruvate Kinase/metabolism
MH  - Ventricular Function
EDAT- 2007/08/25 09:00
MHDA- 2007/11/07 09:00
CRDT- 2007/08/25 09:00
PHST- 2007/04/25 00:00 [accepted]
PHST- 2007/08/25 09:00 [pubmed]
PHST- 2007/11/07 09:00 [medline]
PHST- 2007/08/25 09:00 [entrez]
AID - PBZ007002 [pii]
AID - 10.1086/520129 [doi]
PST - ppublish
SO  - Physiol Biochem Zool. 2007 Sep-Oct;80(5):542-50. doi: 10.1086/520129. Epub 2007 
      Jul 13.