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The effects of orbital spaceflight on bone histomorphometry and messenger ribonucleic acid levels for bone matrix proteins and skeletal signaling peptides in ovariectomized growing ratsA 14-day orbital spaceflight was performed using ovariectomized Fisher 344 rats to determine the combined effects of estrogen deficiency and near weightlessness on tibia radial bone growth and cancellous bone turnover. Twelve ovariectomized rats with established cancellous osteopenia were flown aboard the space shuttle Columbia (STS-62). Thirty ovariectomized rats were housed on earth as ground controls: 12 in animal enclosure modules, 12 in vivarium cages, and 6 killed the day of launch for baseline measurements. An additional 18 ovary-intact rats were housed in vivarium cages as ground controls: 8 rats were killed as baseline controls and the remaining 10 rats were killed 14 days later. Ovariectomy increased periosteal bone formation at the tibia-fibula synostosis; cancellous bone resorption and formation in the secondary spongiosa of the proximal tibial metaphysis; and messenger RNA (mRNA) levels for the prepro-alpha2(1) subunit of type 1 collagen, osteocalcin, transforming growth factor-beta, and insulin-like growth factor I in the contralateral proximal tibial metaphysis and for the collagen subunit in periosteum pooled from tibiae and femora and decreased cancellous bone area. Compared to ovariectomized weight-bearing rats, the flight group experienced decreases in periosteal bone formation, collagen subunit mRNA levels, and cancellous bone area. The flight rats had a small decrease in the cancellous mineral apposition rate, but no change in the calculated bone formation rate. Also, spaceflight had no effect on cancellous osteoblast and osteoclast perimeters or on mRNA levels for bone matrix proteins and signaling peptides. On the other hand, spaceflight resulted in an increase in bone resorption, as ascertained from the diminished retention of a preflight fluorochrome label. This latter finding suggests that osteoclast activity was increased. In a follow-up ground-based experiment, unilateral sciatic neurotomy of ovariectomized rats resulted in cancellous bone loss in the unloaded limb in excess of that induced by gonadal hormone deficiency. This additional bone loss was arrested by estrogen replacement. We conclude from these studies that estrogen alters the expression of signaling peptides believed to mediate skeletal adaptation to changes in mechanical usage and likewise modifies the skeletal response to mechanical unloading.
Document ID
20040172997
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Cavolina, J. M.
(Mayo Clinic Rochester, Minnesota 55905, United States)
Evans, G. L.
Harris, S. A.
Zhang, M.
Westerlind, K. C.
Turner, R. T.
Date Acquired
August 22, 2013
Publication Date
April 1, 1997
Publication Information
Publication: Endocrinology
Volume: 138
Issue: 4
ISSN: 0013-7227
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: AR-41418
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Physiology and Countermeasures
short duration
NASA Discipline Regulatory Physiology
Non-NASA Center
STS-62 Shuttle Project
manned
Flight Experiment
NASA Discipline Number 00-00
NASA Discipline Number 18-10
NASA Program Flight

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