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Growth hormone, IGF-I, and exercise effects on non-weight-bearing fast muscles of hypophysectomized ratsThe effects of growth hormone (GH) or insulin-like growth factor I (IGF-I) with or without exercise (ladder climbing) in countering the effects of unweighting on fast muscles of hypophysectomized rats during 10 days of hindlimb suspension were determined. Compared with untreated suspended rats, muscle weights were 16-29% larger in GH-treated and 5-15% larger in IGF-I-treated suspended rats. Exercise alone had no effect on muscle weights. Compared with ambulatory control, the medial gastrocnemius weight in suspended, exercised rats was larger after GH treatment and maintained with IGF-I treatment. The combination of GH or IGF-I plus exercise in suspended rats resulted in an increase in size of each predominant fiber type, i.e., types I, I + IIa and IIa + IIx, in the medial gastrocnemius compared with untreated suspended rats. Normal ambulation or exercise during suspension increased the proportion of fibers expressing embryonic myosin heavy chain in hypophysectomized rats. The phenotype of the medial gastrocnemius was minimally affected by GH, IGF-I, and/or exercise. These results show that there is an IGF-I, as well as a GH, and exercise interactive effect in maintaining medial gastrocnemius fiber size in suspended hypophysectomized rats.
Document ID
20040172828
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Grossman, E. J.
(NASA Ames Research Center Moffett Field, CA United States)
Grindeland, R. E.
Roy, R. R.
Talmadge, R. J.
Evans, J.
Edgerton, V. R.
Date Acquired
August 22, 2013
Publication Date
November 1, 1997
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 83
Issue: 5
ISSN: 8750-7587
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: NS-16333
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center ARC
NASA Discipline Musculoskeletal

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