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Effects of Growth Hormone/IGF-I and Exercise on Unloaded BonesGrowth hormone (GH) and insulin-like growth factor-I (IGF-I) in combination with exercise prevent muscle atrophy induced by unloading in the tail-suspension rat model for space flight (Gosselink et al, FASEB J 1994). This study evaluated the effects of these treatments on bone. Hypophysectomized rats were suspended (S) and treated with 1mg/kg/day CH plus IGF-I (H) or vehicle (Sal) daily by injection and exercised (Ex) by 3 climbs up a 1m ladder carrying a load equal to 30% the initial body weight (BW) 3x/day for 10 days. Tibial epiphysis (Epi) widths were measured by micrometry and femoral Bone Mineral Content (fBMC) in excised femurs by DEXA (Lunar DPX-L). Serum calcium (Ca) and phosphorus (Pi) were measured by COBAS Autoanalyzer (Roche Diag.). Ambulatory (Amb)-H treated rats showed growth rates of 6.6+-0.9 g/day, similar to S-H-Ex and higher than S-H (3.210.6, p less than 0.05) and S-Sal (-0.711.0, p less than 0.05). Epi widths were 10% lower in S-Sal, and S-Sal-Ex, and increased 100% in all H groups. fBMC was less in S than Amb, only when all S groups are compared to both Amb groups (p less than 0.03). H treatment increased fBMC (p less than 0.05) but reduced fBMC/100g BW in all H groups (p less than 0.001). The reduced density of H bone cannot be attributed to low circulating Ca. and Pi since they were higher in H than Sal (p less than 0.001). H treatment for 10 days in doses sufficient to support normal growth in BW failed to produce normal Epi widths or fBMC, even when combined with exercise. The suspension effect observed in Epi widths was not corrected by H or Ex alone, but was improved by H plus a This regimen. although effective in preventing muscle atrophy, failed to return bone measures, Epi widths and fBMC, to normal.
Document ID
20020014425
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Harper, J. S.
(NASA Ames Research Center Moffett Field, CA United States)
Arnaud, S. B.
(NASA Ames Research Center Moffett Field, CA United States)
Gosselink, K. L.
(NASA Ames Research Center Moffett Field, CA United States)
Grindeland, R. E.
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Aerospace Medicine
Meeting Information
Meeting: American Society for Gravitational and Space Biology 10th Annual Meeting
Location: San Francisco, CA
Country: United States
Start Date: October 19, 1994
End Date: October 22, 1994
Funding Number(s)
PROJECT: RTOP 199-14-12-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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