Characterization and Cloning of a Rat Insulin-Like Growth Factor Binding Protein
The insulin-like growth factors, IGF-I and IGF-II, occur complexed to specific binding proteins in blood and other extracellular fluids.1 IGF-binding protein complexes of 150 kDa predominate in adult human and rat serum2,3, and also have been observed in human and porcine milk 4,5, and human fibroblast conditioned media6,7. Acid pH irreversibly dissociates the 150 kDa binding protein complex into an ~40 kDa acid-stable binding subunit.1 Recently, Baxter8 provided evidence for the existence of a second subunit of ~100 kDa that is unstable at acid pH and does not bind IGFs.
KeywordsHuman Amniotic Fluid Human Cerebrospinal Fluid Ligand Blotting Carboxyl Terminal Region Porcine Milk
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