The presence of classical insulin-like growth factor (IGF) type-I and -II receptors on mouse osteoblasts: autocrine/paracrine growth effect of IGFs?
Specific binding to and proliferative actions of insulin-like growth factors-I and -II (IGF-I and -II) on fetal mouse osteoblasts were tested. Membranes of mouse osteoblasts were shown by binding competition studies to possess specific binding sites for IGF-I and IGF-II. When IGF-I was used as a tracer, half-maximal displacement was obtained with 1.11 micrograms IGF-I/l and with 14 micrograms IGF-II/l. Displacement of 125I-labelled IGF-I was accomplished with 2.33 micrograms IGF-II/l and with 55 micrograms IGF-I/l. Affinity cross-linking showed bands of 130 kDa 125I-labelled IGF-I and 260 kDa 125I-labelled IGF-II under reducing conditions, further indicating the presence of classical type-I and -II receptor sites on mouse osteoblasts. Mitogenic effects of IGFs were weak; a combination with epidermal growth factor or fibroblast growth factor showed strong synergistic action however. The possibility of autocrine/paracrine actions of IGFs is discussed.
Slootweg
M C
MC
University Hospital, Department of Internal Medicine, Research Group for Bone Metabolism, Utrecht, The Netherlands.
Hoogerbrugge
C M
CM
de Poorter
T L
TL
Duursma
S A
SA
van Buul-Offers
S C
SC
D000818:Animals; D001846:Bone Development / Q000502:physiology*; D002478:Cells, Cultured; D002846:Chromatography, Affinity / Q000379:methods; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008938:Mitosis / Q000502:physiology*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin
D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II