Document Detail

Ammonia and amino acid metabolism in skeletal muscle: human, rodent and canine models.
MedLine Citation:
PMID:  9475642     Owner:  NLM     Status:  MEDLINE    
This review considers four experimental models for studying the dynamics of ammonia and amino acid metabolism in skeletal muscle: the rat hindlimb, the isolated dog gastrocnemius, the leg extensor for humans, and the traditional approach of humans performing two-legged exercise. The rat hindlimb is well suited for studying intense exercise with fast-twitch white fibers, but it is poorly suited for studying prolonged exercise because of rapid fatigue of major portions of the muscle and the restrictions of taking multiple blood samples. The traditional human model is limited because of the inability to quantify accurately the active muscle mass and to determine the true blood flow to the entire active tissue. Despite species differences and the various limitations of the paradigms, there are numerous consistencies in the literature. For example, human muscle and the canine gastrocnemius demonstrate similar magnitudes of efflux of ammonia, glutamine, and alanine (when indexed for the active mass) during prolonged exercise. Muscle has a large ammonia producing capacity during either intense or prolonged exercise. In prolonged exercise this is accompanied by similar productions of alanine and glutamine as well as a large uptake of glutamate. Despite the latter, the intramuscular glutamate concentration rapidly declines by more than 50% and remains constant throughout the exercise period. The leg extensor model and the canine gastrocnemius offer the greatest opportunities to quantify these responses during prolonged exercise.
T E Graham; D A MacLean
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  30     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  1998 Jan 
Date Detail:
Created Date:  1998-03-27     Completed Date:  1998-03-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  34-46     Citation Subset:  IM; S    
Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.
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MeSH Terms
Amino Acids / metabolism*
Ammonia / metabolism*
Exercise / physiology*
Exercise Test / methods
Hindlimb / anatomy & histology,  physiology
Knee Joint / anatomy & histology,  physiology
Models, Biological
Muscle Fibers, Fast-Twitch / physiology
Muscle, Skeletal / blood supply,  metabolism*,  physiology
Regional Blood Flow
Reg. No./Substance:
0/Amino Acids; 7664-41-7/Ammonia

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