Alteration of spinal cord IGF-I receptors and skeletal muscle IGF-I after hind-limb immobilization in the rat

Abstract

The effects of 4 weeks' hind-limb immobilization on the spinal cord insulin-like growth factor-I (IGF-I) receptors and skeletal muscle IGF-I level was investigated in rats. Quantitative receptor autoradiography using [125I]IGF-I as a ligand was performed to measure IGF-I receptors in cryosections from the lumbar region of the spinal cord. IGF-I receptor levels were significantly higher in all spinal cord laminae on the side ipsilateral to the immobilized limb than in the same spinal level of the controls. Using radioimmunoassay (RIA), IGF-I levels were significantly low in the soleus (SOL), but not the tibialis anterior (TIB) muscles, compared to the controls. The enhancement of the spinal cord IGF-I receptors after hind-limb immobilization may constitute part of the nervous system response to disuse.