title: Affinity labeled somatomedin-C-binding proteins in rat sera.
abstract: We have developed an affinity labeling technique that uses disuccinimidyl suberate to covalently cross-link [125I]somatomedin-C (Sm-C) to specific binding proteins in rat serum. Normal rat serum contains four major classes of intensely labeled [125I]Sm-C-binding protein complexes which are sensitive to competition with unlabeled Sm-C with relative molecular masses of 95, 49, 36-33, and 26-23 K. In addition, less intensely labeled complexes are observed migrating between 175 and 115 K. Of the Sm-C binding complexes observed in normal serum, hypophysectomized (hypox) serum contains only an intensely labeled 36-33-K complex and a faint 49-K complex. Chronic administration of ovine (100 micrograms, ip, daily) to hypox rats induces the 95-K complex and possibly complexes between 175-115 K. With increasing duration of treatment, these complexes as well as the 49-K complex appear to increase in intensity. Binding proteins in both hypox and normal sera do not appear to distinguish between Sms, since both unlabeled Sm-C and multiplication-stimulating activity were equally potent in competing with [125I]Sm-C for binding. This affinity labeling technique appears to be a useful investigative tool to study the physiology and structure of Sm-binding proteins.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002352:Carrier Proteins / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel; D007016:Hypophysectomy; D018969:Insulin-Like Growth Factor Binding Proteins; D007457:Iodine Radioisotopes; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013388:Succinimides / Q000097:blood*
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007457:Iodine Radioisotopes; D013388:Succinimides; C019358:disuccinimidyl suberate