title: Gastric inhibitory polypeptide (GIP) binding sites in rat brain.
abstract: Synthetic porcine gastric inhibitory polypeptide (GIP) was iodinated and purified by reverse-phase HPLC and used to localize saturable [125I]GIP binding sites by radioligand binding to frozen sections of rat brain followed by autoradiography. Saturable [125I]GIP binding sites were expressed in several brain regions including cerebral cortex, anterior olfactory nucleus, lateral septal nucleus, subiculum, inferior colliculus, and inferior olive. Saturable [125I]GIP binding was time dependent, reversible, high affinity, and specific for GIP. Scatchard analysis of equilibrium binding resulted in an estimated dissociation constant (Kd) of 16-62 pM for the rat brain [125I]GIP binding sites. Peptides with amino acid sequences similar to GIP such as secretin, vasoactive intestinal polypeptide (VIP), glucagon, and peptide histidine isoleucine (PHI) only partially inhibited saturable [125I]GIP binding at concentrations approximately 10,000-100,000-fold higher than GIP. Saturable [125I]GIP binding was not observed in other rat organs surveyed such as spinal cord, pituitary, stomach, small intestine, colon, pancreas, liver, heart, or skeletal muscle. We conclude that a saturable [125I]GIP binding site with the pharmacological properties of an authentic GIP receptor is expressed in certain regions of the rat brain.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, NC 27710.
authors.forename: A M
authors.initials: AM
authors.lastname: Kaplan
authors.forename: S R
authors.initials: SR
authors.lastname: Vigna
mesh_terms: D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism*; D008297:Male; D009479:Neuropeptides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011964:Receptors, Gastrointestinal Hormone / Q000302:isolation & purification*; D014018:Tissue Distribution
chemical_list: D009479:Neuropeptides; D011964:Receptors, Gastrointestinal Hormone; D005749:Gastric Inhibitory Polypeptide; C041086:gastric inhibitory polypeptide receptor