title: Biochemical properties of brain somatostatin receptors.
abstract: The physical properties of brain and pituitary somatostatin receptors were characterized using photocrosslinking techniques. Somatostatin receptors in rat corpus striatum and anterior pituitary membranes were covalently bound to the non-reducible somatostatin analog, [125I]CGP 23996, using the crosslinking agent n-hydroxysuccinimidyl-4-azidobenzoate and ultraviolet light. In striatal membranes, a protein of 60,000 mol. wt was labeled by [125I]CGP 23996. The binding was potently inhibited by somatostatin analogs but not by other biologically active peptides. The labeling of the 60,000 mol. wt protein by [125I]CGP 23996 was diminished by guanine triphosphate gamma thiol, which is consistent with the labeling of a somatostatin receptor coupled to guanine triphosphate binding proteins. The migration of the [125I]CGP 23996 labeled 60,000 mol. wt protein in native sodium dodecyl sulfate-gels was not affected by the reducing agent dithiothreitol, indicating that there is a general lack of disulfide bridges in the striatal somatostatin receptor. The striatal somatostatin receptor was solubilized with the detergent 3-[(3-cholamidopropyl)-dimethylaminoio]-1-propanesulfonate and specifically bound to the lectin wheat germ agglutinin, suggesting that the striatal somatostatin receptor is a glycoprotein. [125I]CGP 23996 also labeled a 60,000 mol. wt protein in anterior pituitary membranes. The characteristics of [125I]CGP 23996 binding to anterior pituitary membranes were consistent with the labeling of a somatostatin receptor. Interestingly, a comparison of the [125I]CGP 23996 labeled material from striatal and anterior pituitary membranes by two-dimensional polyacrylamide gel electrophoresis revealed the presence of several striatal somatostatin receptors of varying charge (pI values between 6 and 6.5) but only a single pituitary receptor. These findings indicate that physical differences may exist between subtypes of somatostatin receptors.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104.
authors.forename: K
authors.initials: K
authors.lastname: Thermos
authors.forename: H T
authors.initials: HT
authors.lastname: He
authors.forename: H L
authors.initials: HL
authors.lastname: Wang
authors.forename: N
authors.initials: N
authors.lastname: Margolis
authors.forename: T
authors.initials: T
authors.lastname: Reisine
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism*; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013004:Somatostatin; C038136:CGP 23996