title: Common or distinct receptors for gastrin and cholecystokinin in gastric mucosa?
abstract: The differentiation between gastrin (HG) and cholecystokinin (CCK) receptors in gastric mucosa was examined on isolated parietal (F3) and non-parietal (F1) cells from rabbit fundic mucosa separated by elutriation. Direct binding assays on enriched cell populations were performed using 125I-labeled HG-17, 125I-labeled CCK-8 and 125I-labeled CCK-39 as probes. (1) On F1 cells, the dissociation constants (Kd) for the two labeled CCKs were nearly the same (62 pM for CCK-8 and 74 pM for CCK-39) but the binding capacity for CCK-8 was 2-times higher than for CCK-39. HG-17 also bound to this cell population, but its Kd value as about 2-times higher (110 pM) than that of CCK. The presence of two distinct classes of sites on F1 cells can be suggested from competition studies: one more specific for CCK, which bound CCK-8 and CCK-39 with the same affinity, and another class more specific for gastrin, which bound CCK-8 and HG-17 with the same affinity and CCK-39 with a low affinity. (2) On F3 cells, CCK-8 and HG-17 bound with similar affinities (Kd values 81 pM for CCK-8 and 87 pM for HG-17), but CCK-39 did not specifically bind to this cell population. The presence of a binding site more specific for HG than for CCK on F3 cells was confirmed by competition studies in which CCK-33 competed for binding with labeled HG-17 and labeled CCK-8 with a 50-times lower affinity than the other peptides.
authors.affiliation: Laboratoire de Biochimie des Membranes du LP 8402 CNRS, INSERM U 249, Faculté de Pharmacie, Montpellier, France.
authors.forename: R
authors.initials: R
authors.lastname: Magous
authors.forename: J C
authors.initials: JC
authors.lastname: Galleyrand
authors.forename: J P
authors.initials: JP
authors.lastname: Bali
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D005753:Gastric Mucosa / Q000032:analysis*; D066298:In Vitro Techniques; D011817:Rabbits; D011949:Receptors, Cholecystokinin / Q000032:analysis*
chemical_list: D011949:Receptors, Cholecystokinin