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Maintenance of myonuclear domain size in rat soleus after overload and growth hormone/IGF-I treatmentThe purpose of this study was to determine the effects of functional overload (FO) combined with growth hormone/insulin-like growth factor I (GH/IGF-I) administration on myonuclear number and domain size in rat soleus muscle fibers. Adult female rats underwent bilateral ablation of the plantaris and gastrocnemius muscles and, after 7 days of recovery, were injected three times daily for 14 days with GH/IGF-I (1 mg/kg each; FO + GH/IGF-I group) or saline vehicle (FO group). Intact rats receiving saline vehicle served as controls (Con group). Muscle wet weight was 32% greater in the FO than in the Con group: 162 +/- 8 vs. 123 +/- 16 mg. Muscle weight in the FO + GH/IGF-I group (196 +/- 14 mg) was 59 and 21% larger than in the Con and FO groups, respectively. Mean soleus fiber cross-sectional area of the FO + GH/IGF-I group (2,826 +/- 445 microm2) was increased compared with the Con (2,044 +/- 108 microm2) and FO (2,267 +/- 301 microm2) groups. The difference in fiber size between the FO and Con groups was not significant. Mean myonuclear number increased in FO (187 +/- 15 myonuclei/mm) and FO + GH/IGF-I (217 +/- 23 myonuclei/mm) rats compared with Con (155 +/- 12 myonuclei/mm) rats, although the difference between FO and FO + GH/IGF-I animals was not significant. The mean cytoplasmic volume per myonucleus (myonuclear domain) was similar across groups. These results demonstrate that the larger mean muscle weight and fiber cross-sectional area occurred when FO was combined with GH/IGF-I administration and that myonuclear number increased concomitantly with fiber volume. Thus there appears to be some mechanism(s) that maintains the myonuclear domain when a fiber hypertrophies.
Document ID
20040172711
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
McCall, G. E.
(Department of Physiological Science California 94080, United States)
Allen, D. L.
Linderman, J. K.
Grindeland, R. E.
Roy, R. R.
Mukku, V. R.
Edgerton, V. R.
Date Acquired
August 22, 2013
Publication Date
April 1, 1998
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 84
Issue: 4
ISSN: 8750-7587
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NS-16333
CONTRACT_GRANT: DE-07212
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Musculoskeletal
Non-NASA Center
NASA Center ARC

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