QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online April 23, 2004
Journal of Experimental Biology 207, 1865-1874 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00965

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Clow, K. A. Articles by Driedzic, W. R. Search for Related Content PubMed PubMed Citation Articles by Clow, K. A. Articles by Driedzic, W. R.

The regulation and importance of glucose uptake in the isolated Atlantic cod heart: rate-limiting steps and effects of hypoxia

Kathy A. Clow¹, Kenneth J. Rodnick², Tyson J. MacCormack¹ and William R. Driedzic^1,*

¹ Ocean Sciences Centre, Memorial University of Newfoundland, St John's, Newfoundland, Canada, A1C 5S7
² Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007, USA

^* Author for correspondence (e-mail: wdriedzic{at}mun.ca)

Accepted 8 March 2004

This study investigated the regulation of glucose uptake in Atlantic cod (Gadus morhua) hearts. Isolated hearts were perfused with or without glucose in the medium, under either normoxic or severely hypoxic conditions. Working at basal levels, hearts did not require extracellular glucose to maintain power under aerobic conditions. However, cardiac performance was significantly reduced without exogenous glucose under oxygen-limiting conditions. The addition of the glucose transporter inhibitor cytochalasin B caused hypoxic hearts to fail early, and hearts perfused with a glucose analogue, 2-deoxyglucose (2-DG), increased glucose uptake 3-fold under hypoxia. The uptake of 2-DG was only partially inhibited when cytochalasin B was added to the medium. Isolated ventricle strips were also incubated in the presence of 2-DG and the extracellular marker mannitol. Glucose uptake (glucose transport plus intracellular phosphorylation) was assessed by measuring the initial rate of 2-deoxyglucose-6-phosphate (2-DG-6-P) accumulation. At 1 mmol l^-1 2-DG, the rate of 2-DG uptake remained linear for 60 min, and 2-DG-6-P, but not free 2-DG, accumulation was increased. The fact that intracellular 2-DG did not increase indicates that glucose transport is the rate-limiting step for glucose utilization in non-stimulated cardiac tissue. Replacement of Na⁺ by choline in the incubation medium did not affect 2-DG uptake, providing evidence that Na⁺-coupled glucose transport is absent in cod cardiac tissue. Similar to cytochalasin B, glucose uptake was also inhibited by phloridzin, suggesting that facilitated, carrier-mediated glucose transport occurs in cod hearts. Under the conditions employed in these experiments, it is clear that (1) activation of glucose transport is required to support hypoxic performance, (2) the rate-limiting step for glucose utilization is glucose transport rather than glucose phosphorylation, (3) 2-DG uptake accurately reflects glucose transport activity and (4) glucose uptake in cod hearts does not involve an Na⁺-dependent mechanism.

Key words: glucose uptake, glucose transport, cytochalasin B, 2-deoxyglucose, hypoxia, heart, cardiac performance, cod, Gadus morhua

This article has been cited by other articles:

				P. K. Battiprolu, K. J. Harmon, and K. J. Rodnick Sex differences in energy metabolism and performance of teleost cardiac tissue Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R827 - R836. [Abstract] [Full Text] [PDF]

				T. J. MacCormack and W. R. Driedzic The impact of hypoxia on in vivo glucose uptake in a hypoglycemic fish, Myoxocephalus scorpius Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R1033 - R1042. [Abstract] [Full Text] [PDF]

				J. R. Hall, C. E. Short, and W. R. Driedzic Sequence of Atlantic cod (Gadus morhua) GLUT4, GLUT2 and GPDH: developmental stage expression, tissue expression and relationship to starvation-induced changes in blood glucose J. Exp. Biol., November 15, 2006; 209(22): 4490 - 4502. [Abstract] [Full Text] [PDF]

				R. S. Farrar, P. K. Battiprolu, N. S. Pierson, and K. J. Rodnick Steroid-induced cardiac contractility requires exogenous glucose, glycolysis and the sarcoplasmic reticulum in rainbow trout J. Exp. Biol., June 1, 2006; 209(11): 2114 - 2128. [Abstract] [Full Text] [PDF]

				J. R. Hall, T. J. MacCormack, C. A. Barry, and W. R. Driedzic Sequence and expression of a constitutive, facilitated glucose transporter (GLUT1) in Atlantic cod Gadus morhua J. Exp. Biol., December 15, 2004; 207(26): 4697 - 4706. [Abstract] [Full Text] [PDF]