title: Effects of short- and long-term rat hind limb immobilization on spinal cord insulin-like growth factor-I and its receptor.
abstract: In this study we investigated changes in the spinal cord insulin-like growth factor-I peptide (IGF-I) and its receptors (IGF-IR) after hind limb immobilization for 5 days, 2, 4, and 8 weeks. Moreover, effects on IGF-I and nicotinic cholinergic receptors (nAChRs) in two types of skeletal muscle were also investigated. IGF-I levels were measured by radioimmunoassay (RIA) whereas IGF-IR and nAChRs were measured by quantitative receptor autoradiography. Spinal cord IGF-I levels decreased significantly after 5 days, 2 and 4 weeks of immobilization, whereas IGF-IR increased significantly after 4 and 8 weeks compared to controls. In skeletal muscles, nAChRs increased significantly after 5 days and 2 weeks in the soleus (SOL) and tibialis anterior (TIB) muscles, respectively, and continued up to 8 weeks in both muscles. IGF-I concentration decrease significantly after 4 and 8 weeks in the SOL and TIB muscles, respectively. Despite the normal levels of IGF-I in both muscles at the early time points (5 days and 2 weeks), low levels of IGF-I were observed concurrently in the spinal cord ipsilateral to the immobilized limb. Our findings suggest that the early decrease in the IGF-I level and the late upregulation in the IGF-IR in the spinal cord might represent a nervous system response to disuse.
authors.affiliation: Department of Orthopedic Surgery, Division of Geriatric Medicine, Karolinska Institute, Huddinge University Hospital, S-141 86 Huddinge, Stockholm, Sweden. isam_suliman@hotmail.com
authors.forename: I A
authors.initials: IA
authors.lastname: Suliman
authors.forename: J U
authors.initials: JU
authors.lastname: Lindgren
authors.forename: A M
authors.initials: AM
authors.lastname: Elhassan
authors.forename: K M
authors.initials: KM
authors.lastname: Diab
authors.forename: A
authors.initials: A
authors.lastname: Adem
mesh_terms: D000818:Animals; D001345:Autoradiography; D002908:Chronic Disease; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism* / Q000503:physiopathology; D020966:Muscular Disorders, Atrophic / Q000378:metabolism* / Q000503:physiopathology; D009929:Organ Size / Q000502:physiology; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012149:Restraint, Physical; D013116:Spinal Cord / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
chemical_list: D011978:Receptors, Nicotinic; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1