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Skeletal unloading induces selective resistance to the anabolic actions of growth hormone on boneLoss of skeletal weight bearing or physical unloading of bone in the growing animal inhibits bone formation and induces a bone mineral deficit. To determine whether the inhibition of bone formation induced by skeletal unloading in the growing animal is a consequence of diminished sensitivity to growth hormone (GH) we studied the effects of skeletal unloading in young hypophysectomized rats treated with GH (0, 50, 500 micrograms/100 g body weight/day). Skeletal unloading reduced serum osteocalcin, impaired uptake of 3H-proline into bone, decreased proximal tibial mass, and diminished periosteal bone formation at the tibiofibular junction. When compared with animals receiving excipient alone, GH administration increased bone mass in all animals. The responses in serum osteocalcin, uptake of 3H-proline and 45Ca into the proximal tibia, and proximal tibial mass in non-weight bearing animals were equal to those in weight bearing animals. The responses in trabecular bone volume in the proximal tibia and bone formation at the tibiofibular junction to GH, however, were reduced significantly by skeletal unloading. Bone unloading prevented completely the increase in metaphyseal trabecular bone normally induced by GH and severely dampened the stimulatory effect (158% vs. 313%, p < 0.002) of GH on periosteal bone formation. These results suggest that while GH can stimulate the overall accumulation of bone mineral in both weight bearing and non-weight bearing animals, skeletal unloading selectively impairs the response of trabecular bone and periosteal bone formation to the anabolic actions of GH.
Document ID
20050000159
Document Type
Reprint (Version printed in journal)
Authors
Halloran, B. P. (University of California San Francisco, United States)
Bikle, D. D.
Harris, J.
Autry, C. P.
Currier, P. A.
Tanner, S.
Patterson-Buckendahl, P.
Morey-Holton, E.
Date Acquired
August 22, 2013
Publication Date
August 1, 1995
Publication Information
Publication: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research
Volume: 10
Issue: 8
ISSN: 0884-0431
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Number 40-40
NASA Program Space Biology
NASA Program Space Physiology and Countermeasures
NASA Discipline Number 26-10
NASA Center ARC
NASA Discipline Musculoskeletal