Document Detail

Autoregulation of myocardial glycogen concentration during intermittent hypoxia.
MedLine Citation:
PMID:  8770128     Owner:  NLM     Status:  MEDLINE    
During hypoxia, the heart consumes glycogen to generate ATP. Tolerance of repetitive hypoxia logically requires prompt replenishment of glycogen, a process whose regulation is not fully understood. To examine this, we imposed a defined hypoxic stimulus on the rat heart while varying its workload. In intact rats, hypoxia reduced myocardial glycogen approximately 30% and increased both the fraction of glycogen synthase in its physiologically active (GS I) form (from 0.24 +/- 0.06 to 0.82 +/- 0.07; P < 0.005) and glycogen synthesis (from 0.087 +/- 0.011 to 0.375 +/- 0.046 mumol.g-1.min-1; P < 0.005). Reducing cardiac work (with propranolol or heterotopic transplantation) reduced glycogen breakdown, glycogen synthase activation, and glycogen synthesis in parallel, stepwise fashion in intact rats. Correspondingly, hypoxia increased GS I activity in the perfused heart in vitro, but only under conditions where glycogen was consumed. This suggests myocardial glycogen synthase is activated by systemic hypoxia and catalyzes rapid posthypoxic glycogen synthesis. Hypoxic glycogen synthase activation appears to be a proportionate, wholly intrinsic response to local glycogenolysis, operating to preserve myocardial glycogen stores independent of any extracardiac mediator of carbohydrate metabolism.
P H McNulty; C Ng; W X Liu; D Jagasia; G V Letsou; J C Baldwin; R Soufer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  271     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1996 Aug 
Date Detail:
Created Date:  1996-10-30     Completed Date:  1996-10-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R311-9     Citation Subset:  IM    
Department of Internal Medicine, Veterans Affairs Medical Center, West Haven, Connecticut, USA.
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MeSH Terms
Anoxia / blood,  physiopathology*
Blood Pressure / drug effects
Gases / blood
Glucose-6-Phosphate / metabolism
Glycogen / metabolism*
Glycogen Synthase / metabolism
Heart Rate / drug effects
Heart Transplantation
Insulin / blood
Myocardial Contraction
Myocardium / metabolism*
Osmolar Concentration
Oxygen / pharmacology
Propranolol / pharmacology
Rats, Sprague-Dawley
Reg. No./Substance:
0/Gases; 11061-68-0/Insulin; 525-66-6/Propranolol; 56-73-5/Glucose-6-Phosphate; 7782-44-7/Oxygen; 9005-79-2/Glycogen; EC Synthase

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