Document Detail

Regulation of glycogen phosphorylase and PDH during exercise in human skeletal muscle during hypoxia.
MedLine Citation:
PMID:  10710508     Owner:  NLM     Status:  MEDLINE    
The present study examined the acute effects of hypoxia on the regulation of skeletal muscle metabolism at rest and during 15 min of submaximal exercise. Subjects exercised on two occasions for 15 min at 55% of their normoxic maximal oxygen uptake while breathing 11% O(2) (hypoxia) or room air (normoxia). Muscle biopsies were taken at rest and after 1 and 15 min of exercise. At rest, no effects on muscle metabolism were observed in response to hypoxia. In the 1st min of exercise, glycogenolysis was significantly greater in hypoxia compared with normoxia. This small difference in glycogenolysis was associated with a tendency toward a greater concentration of substrate, free P(i), in hypoxia compared with normoxia. Pyruvate dehydrogenase activity (PDH(a)) was lower in hypoxia at 1 min compared with normoxia, resulting in a reduced rate of pyruvate oxidation and a greater lactate accumulation. During the last 14 min of exercise, glycogenolysis was greater in hypoxia despite a lower mole fraction of phosphorylase a. The greater glycogenolytic rate was maintained posttransformationally through significantly higher free [AMP] and [P(i)]. At the end of exercise, PDH(a) was greater in hypoxia compared with normoxia, contributing to a greater rate of pyruvate oxidation. Because of the higher glycogenolytic rate in hypoxia, the rate of pyruvate production continued to exceed the rate of pyruvate oxidation, resulting in significant lactate accumulation in hypoxia compared with no further lactate accumulation in normoxia. Hence, the elevated lactate production associated with hypoxia at the same absolute workload could in part be explained by the effects of hypoxia on the activities of the rate-limiting enzymes, phosphorylase and PDH, which regulate the rates of pyruvate production and pyruvate oxidation, respectively.
M L Parolin; L L Spriet; E Hultman; M G Hollidge-Horvat; N L Jones; G J Heigenhauser
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  American journal of physiology. Endocrinology and metabolism     Volume:  278     ISSN:  0193-1849     ISO Abbreviation:  Am. J. Physiol. Endocrinol. Metab.     Publication Date:  2000 Mar 
Date Detail:
Created Date:  2000-05-24     Completed Date:  2000-05-24     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  100901226     Medline TA:  Am J Physiol Endocrinol Metab     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  E522-34     Citation Subset:  IM; S    
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
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MeSH Terms
Adenosine Triphosphate / metabolism
Anoxia / blood,  enzymology*,  physiopathology
Carnitine / metabolism
Coenzyme A / metabolism
Energy Metabolism
Exercise / physiology*
Glycogen / metabolism
Heart / physiology
Lactic Acid / metabolism
Muscle, Skeletal / enzymology*
Phosphates / metabolism
Phosphorylases / metabolism*
Pyruvate Dehydrogenase Complex / metabolism*
Pyruvic Acid / metabolism
Reg. No./Substance:
0/Phosphates; 0/Pyruvate Dehydrogenase Complex; 127-17-3/Pyruvic Acid; 50-21-5/Lactic Acid; 541-15-1/Carnitine; 56-65-5/Adenosine Triphosphate; 85-61-0/Coenzyme A; 9005-79-2/Glycogen; EC 2.4.1.-/Phosphorylases

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