Persistent Link:
http://hdl.handle.net/10150/186136
Title:
Protein metabolism in unweighting atrophy.
Author:
Munoz, Kathryn Anne
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The weightless environment results in atrophy of the anti-gravity muscles. Hindlimb suspension is a model for weightlessness induced atrophy. This study evaluated the effects of hindlimb suspension, microgravity and exercise training followed by suspension on skeletal muscle. Soleus mass, myofibrillar and sarcoplasmic protein content were measured in one to four day hindlimb suspended animals. Protein synthesis was measured by intramuscular injection of ³H phenylalanine with correction for the difference between tRNA and intracellular specific activities. Myofibrillar protein loss was minimal after two days of unweighting but significant after three days. Although sarcoplasmic protein content showed no change, synthesis of both protein pools declined in parallel. Myofibrillar degradation increased during the first three days of unweighting, partially accounting for protein loss. The decline in degradation during day four explained the slower rate of protein loss at this time. Sarcoplasmic protein degradation increased slightly during the first two days of unweighting then declined sharply, thus explaining the sparing of sarcoplasmic proteins. Animals exposed to weightlessness showed soleus atrophy similar to suspended animals. The plantaris and gastrocnemius had reduced growth while the extensor digitorum longus and tibialis anterior grew normally in flight and suspended animals. Insulin stimulated glucose uptake was enhanced in soleus, but not extensor digitorum longus of flight and suspended animals. In situ insulin and IGF-1 stimulated 2-deoxyglucose uptake was greater after six days of suspension. Voluntary wheel training increased soleus mass, protein content and in vivo protein synthesis which plateaued by three weeks. Suspended or trained-suspended animals showed reductions in soleus mass, protein content and synthesis compared to trained animals. However, trained-suspended animals showed higher values for protein content and synthesis compared to suspended animals. In conclusion, these studies show that unweighting atrophy is characterized by decreased synthesis and increased degradation of myofibrillar proteins, and a sparing of sarcoplasmic proteins due to slower degradation. Tail-cast hindlimb suspension may be used as a ground based model to mimic the effects of weightlessness on muscle proteins. Wheel training causes muscle hypertrophy; and although training prior to suspension provides some protection against protein loss, it does not prevent atrophy.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Physiology.; Biochemistry.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Nutritional Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Tischler, Marc E.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleProtein metabolism in unweighting atrophy.en_US
dc.creatorMunoz, Kathryn Anneen_US
dc.contributor.authorMunoz, Kathryn Anneen_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe weightless environment results in atrophy of the anti-gravity muscles. Hindlimb suspension is a model for weightlessness induced atrophy. This study evaluated the effects of hindlimb suspension, microgravity and exercise training followed by suspension on skeletal muscle. Soleus mass, myofibrillar and sarcoplasmic protein content were measured in one to four day hindlimb suspended animals. Protein synthesis was measured by intramuscular injection of ³H phenylalanine with correction for the difference between tRNA and intracellular specific activities. Myofibrillar protein loss was minimal after two days of unweighting but significant after three days. Although sarcoplasmic protein content showed no change, synthesis of both protein pools declined in parallel. Myofibrillar degradation increased during the first three days of unweighting, partially accounting for protein loss. The decline in degradation during day four explained the slower rate of protein loss at this time. Sarcoplasmic protein degradation increased slightly during the first two days of unweighting then declined sharply, thus explaining the sparing of sarcoplasmic proteins. Animals exposed to weightlessness showed soleus atrophy similar to suspended animals. The plantaris and gastrocnemius had reduced growth while the extensor digitorum longus and tibialis anterior grew normally in flight and suspended animals. Insulin stimulated glucose uptake was enhanced in soleus, but not extensor digitorum longus of flight and suspended animals. In situ insulin and IGF-1 stimulated 2-deoxyglucose uptake was greater after six days of suspension. Voluntary wheel training increased soleus mass, protein content and in vivo protein synthesis which plateaued by three weeks. Suspended or trained-suspended animals showed reductions in soleus mass, protein content and synthesis compared to trained animals. However, trained-suspended animals showed higher values for protein content and synthesis compared to suspended animals. In conclusion, these studies show that unweighting atrophy is characterized by decreased synthesis and increased degradation of myofibrillar proteins, and a sparing of sarcoplasmic proteins due to slower degradation. Tail-cast hindlimb suspension may be used as a ground based model to mimic the effects of weightlessness on muscle proteins. Wheel training causes muscle hypertrophy; and although training prior to suspension provides some protection against protein loss, it does not prevent atrophy.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectPhysiology.en_US
dc.subjectBiochemistry.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineNutritional Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairTischler, Marc E.en_US
dc.contributor.committeememberAllen, Ronald E.en_US
dc.contributor.committeememberStini, Williamen_US
dc.contributor.committeememberBrannon, Patsy M.en_US
dc.contributor.committeememberHenriksen, Erik J.en_US
dc.identifier.proquest9322637en_US
dc.identifier.oclc715365120en_US
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