Document Detail

Regulation of muscle glycogen phosphorylase activity following short-term endurance training.
MedLine Citation:
PMID:  8779956     Owner:  NLM     Status:  MEDLINE    
The purpose of this study was to examine the regulation (hormonal, substrate, and allosteric) of muscle glycogen phosphorylase (Phos) activity and glycogenolysis after short-term endurance training. Eight untrained males completed 6 days of cycle exercise (2 h/day) at 65% of maximal O2 uptake (Vo2max). Before and after training subjects cycled for 15 min at 80% of Vo2max, and muscle biopsies and blood samples were obtained at 0 and 30 s, 7.5 and 15 min, and 0, 5, 10, and 15 min of exercise. Vo2max was unchanged with training but citrate synthase (CS) activity increased by 20%. Muscle glycogenolysis was reduced by 42% during the 15-min exercise challenge following training (198.8 +/- 36.9 vs. 115.4 +/- 25.1 mmol/kg dry muscle), and plasma epinephrine was blunted at 15 min of exercise. The Phos a mole fraction was unaffected by training. Muscle phosphocreatine utilization and free Pi and AMP accumulations were reduced with training at 7.5 and 15 min of exercise. It is concluded that posttransformational control of Phos, exerted by reductions in substrate (free Pi) and allosteric modulator (free AMP) contents, is responsible for a blunted muscle glycogenolysis after 6 days of endurance training. The increase in CS activity suggests that the reduction of muscle glycogenolysis was due in part to an enhanced mitochondrial potential.
A Chesley; G J Heigenhauser; L L Spriet
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  270     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1996 Feb 
Date Detail:
Created Date:  1996-12-20     Completed Date:  1996-12-20     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:  E328-35     Citation Subset:  IM    
Department of Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.
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MeSH Terms
Blood / metabolism
Glycogen / metabolism
Lactic Acid / metabolism
Muscles / metabolism*
Phosphorylase a / metabolism
Phosphorylase b / metabolism
Phosphorylases / metabolism*
Physical Education and Training*
Physical Endurance*
Time Factors
Reg. No./Substance:
50-21-5/Lactic Acid; 9005-79-2/Glycogen; EC 2.4.1.-/Phosphorylase a; EC 2.4.1.-/Phosphorylase b; EC 2.4.1.-/Phosphorylases

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