Changes in tissue levels of growth hormone, insulin-like growth factor-I, and somatostatin in the femurs of hind-limb immobilized rats.
Immobilization of an extremity causes skeletal muscle atrophy and a dramatic increase in bone resorption. Growth hormone (GH) is known to play an important role in bone remodeling mediated in part by local insulin-like growth factor-I (IGF-I). In this study, we investigated changes in the levels of GH and IGF-I peptide in bone extracts from the femur after hind-limb immobilization for 5 days, 2, 4, and 8 weeks. The levels of somatostatin, which interacts with GH, were also measured in the bone extracts. GH levels increased after 8 weeks of hind-limb immobilization whereas the IGF-I concentrations increased after 2 weeks, but returned to control levels at 4 weeks, and decreased after 8 weeks of immobilization. The somatostatin levels in the bone extracts increased only after 8 weeks of hind-limb immobilization. Our findings suggest that, after hind-limb immobilization, changes in the concentrations of GH, IGF-I, and somatostatin in bone may mediate bone resorption either directly or through interaction with other factors.
Suliman
I A
IA
Department of Orthopedic Surgery, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden. Isam.Suliman@kfcmail.hs.sll.se
Elhassan
A M
AM
Adem
A
A
El-Bakri
N K
NK
Lindgren
J U
JU
D000704:Analysis of Variance; D000818:Animals; D005269:Femur / Q000378:metabolism*; D013006:Growth Hormone / Q000032:analysis / Q000378:metabolism*; D006614:Hindlimb; D007103:Immobilization; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000032:analysis / Q000378:metabolism*; D013997:Time Factors
D013004:Somatostatin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone