Insulin-like growth factor I receptors on blood cells: their relationship to circulating total and "free" IGF-I, IGFBP-1, IGFBP-3 and insulin levels in healthy subjects.
The relationships between the insulin-like growth factor I/insulin-like growth factor binding protein (IGF-I/IGFBP) system and the IGF-I receptor characteristics on erythrocytes and PBMCs in healthy subjects in the fasting state were studied to establish whether this would be a valid way of examining IGF-I receptors in vivo. The K(d) of the IGF-I receptor on erythrocytes was positively related to circulating "free" IGF-I levels. For the IGF-I receptor on PBMCs no relationship was observed with "free" IGF-I levels. IGFBP-3 levels were inversely related to the number of IGF-I binding sites on erythrocytes and to the K(d) of the IGF-I receptor on PBMCs. Total IGF-I, insulin and IGFBP-1 levels showed no relation to the IGF-I receptor on erythrocytes and PBMCs in the fasting state. This report suggests that studies of IGF-I receptor characteristics on erythrocytes and PBMCs in the fasting state are cell-specific and cannot be extrapolated to other cell types, which may be more relevant target tissues for IGF-I action in vivo.
Janssen
J A
JA
Department of Internal Medicine III, Erasmus University, Rotterdam, The Netherlands.
Uitterlinden
P
P
Hofland
L J
LJ
Lamberts
S W
SW
D000328:Adult; D001667:Binding, Competitive; D001773:Blood Cells / Q000737:chemistry*; D004910:Erythrocyte Membrane / Q000737:chemistry; D004912:Erythrocytes / Q000737:chemistry; D005215:Fasting / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007700:Kinetics; D007963:Leukocytes, Mononuclear / Q000737:chemistry; D008875:Middle Aged; D017526:Receptor, IGF Type 1 / Q000097:blood*; D012016:Reference Values
D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1