title: Characterization of cholecystokinin receptors on the sphincter of Oddi.
abstract: To characterize directly the ability of cholecystokinin (CCK) to interact with receptors on the sphincter of Oddi (SO), we measured binding of 125I-labeled Bolton-Hunter-labeled COOH-terminal octapeptide of cholecystokinin (125I-BH-CCK-8) to tissue sections from the guinea pig SO. Autoradiography localized binding of 125I-BH-CCK-8 over the SO smooth muscle layer. Binding was saturable, specific, dependent on time, pH, and temperature, and was reversible. Binding of 125I-BH-CCK-8 was inhibited by various CCK receptor agonists with the following potencies: CCK-8 much greater than des(SO3)CCK-8 much greater than gastrin-17-I and by various CCK receptor antagonists with the following potencies: L-364,718 greater than proglumide analogue 10 much greater than carbobenzoxy-Tyr(SO3H)-Met-Gly-Trp-Met-Asp-NH2 greater than N2,O2' dibutyryl guanosine 3',5'-cyclic monophosphate. The potencies of agonists in stimulating and of antagonists in inhibiting CCK-8-stimulated SO contractions correlated closely with their abilities to inhibit binding of 125I-BH-CCK-8. Analysis of binding of 125I-BH-CCK-8 to SO tissue sections revealed two classes of CCK binding sites: a high-affinity site [dissociation constant (Kd) 0.2 nM] and a low-affinity site (Kd 70 nM). Atropine or tetrodotoxin (TTX) caused a similar rightward shift of the CCK-8 dose-response curve for stimulation of SO contraction. Comparison of receptor occupation to CCK-8-induced contraction suggested that CCK-8 occupation of the high-affinity binding site correlated with contraction in the absence of atropine and the low-affinity CCK binding with contraction in the presence of atropine or TTX.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: K L
authors.initials: KL
authors.lastname: Cox
authors.forename: T
authors.initials: T
authors.lastname: von Schrenck
authors.forename: T H
authors.initials: TH
authors.lastname: Moran
authors.forename: J D
authors.initials: JD
authors.lastname: Gardner
authors.forename: R T
authors.initials: RT
authors.lastname: Jensen
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001667:Binding, Competitive; D004386:Duodenum / Q000502:physiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D012844:Sincalide / Q000378:metabolism; D009803:Sphincter of Oddi / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D011949:Receptors, Cholecystokinin; D013779:Tetrodotoxin; D001285:Atropine; D012844:Sincalide