Spaceflight modulates insulin-like growth factor binding proteins and glucocorticoid receptor in osteoblasts.
Rat osteoblasts were cultured for 4 or 5 days during a Space Shuttle mission. After 20-h treatment with 1alpha,25-dihydroxyvitamin D3, conditioned media were harvested and cellular DNA and/or RNA were fixed on board. The insulin-like growth factor binding protein (IGF BP)-3 levels in the media were three- and tenfold higher than in ground controls on the fourth and fifth flight days, as quantitated by Western ligand blotting and radioimmunoassay, respectively. The increased IGF BP-3 protein levels correlated with two- to threefold elevation of IGF BP-3 mRNA levels, obtained by reverse transcription-polymerase chain reaction. The IGF BP-5 mRNA levels in flight cultures were 33-69% lower than in ground controls. The IGF BP-4 mRNA levels in flight cultures were 75% lower than in ground controls on the fifth day but were not different on the fourth day. The glucocorticoid receptor mRNA levels in flight cultures were increased by three- to eightfold on the fourth and fifth days compared with levels in ground controls. These data suggest potential mechanisms underlying spaceflight-induced osteopenia.
Kumei
Y
Y
Faculty of Dentistry, Tokyo Medical and Dental University, Tokyo 113-8549, Japan. kumei.det2@dent.tmd.ac.jp
Shimokawa
H
H
Katano
H
H
Akiyama
H
H
Hirano
M
M
Mukai
C
C
Nagaoka
S
S
Whitson
P A
PA
Sams
C F
CF
D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D010006:Osteoblasts / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects*
D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D004247:DNA