Somatostatin binding factor from chicken pancreas.
A soluble somatostatin binding factor was detected in cell-free extracts from chicken pancreas. For binding measurements Tyr1-somatostatin was radio-labeled with 125I by the lactoperoxidase technique. Specific radioactivity of about 18.5 MBq/nmol was achieved. Maximal total binding is approximately 0.17 (B/T) in the presence of 30 mg/l pancreatic protein. The specific binding is 0.10 and is suppressed by addition of 1 mg/l synthetic cold cyclic somatostatin. The dose-response curve of synthetic cyclic somatostatin is in the range of 0.6-600 nmol/l. Ca2+ and reduced thiol-reagents inhibit the specific binding. Insulin, glucagon and corticotropin show a low, and luliberin and reduced somatostatin a high cross-reactivity. Molecular weight was estimated by gel filtration and the specific binding molecule was eluted at a Kav = 0.2 on an Ultrogel (AcA 54) column. This corresponds to Mr 40 000. Electrophoretic properties of the binding complex and semipurification by polyacrylamide disc gel electrophoresis: relative mobility of the 125I-Tyr-somatostatin binding complex is about 0.6. Relative mobilities of binding-protein fractions are 0.71 and 0.74. Highest relative specific binding was detected in the (100 000 g) cytosol fractions. Binding with cell-free extracts from the splenic lobe area was 4-fold higher than that from other parts of the chicken pancreas.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002474:Cell-Free System; D002645:Chickens; D004229:Dithiothreitol / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007515:Islets of Langerhans / Q000032:analysis*; D011956:Receptors, Cell Surface / Q000032:analysis*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000031:analogs & derivatives / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D017481:Receptors, Somatostatin; D014443:Tyrosine; D013004:Somatostatin; C012088:somatostatin, N-Tyr(1)-; D004492:Edetic Acid; D005978:Glutathione; D002118:Calcium; D004229:Dithiothreitol