Characterization of cholecystokinin receptor sites in guinea-pig cortical membranes using (/sup 125/I)Bolton Hunter-cholecystokinin octapeptide

Journal Article · Thu Feb 28 23:00:00 EST 1985 · J. Pharmacol. Exp. Ther.; (United States)

OSTI ID:5483392

Lin, C W; Miller, T

(/sup 125/I)Bolton Hunter-cholecystokinin octapeptide (BH-CCK8) has been prepared using a modified method and was used to study putative cholecystokinin (CCK) receptor sites in the guinea-pig cerebral cortex. Specific binding of (/sup 125/I)BH-CCK8, defined as the difference in binding in the absence and presence of 10(-6) M CCK8, was 70% of total binding. In saturation experiments, the apparent dissociation constant (K/sub d/) was 1 nM and total binding capacity was 28 fmol/mg of protein. In association experiments, conducted at 30 degrees C, binding of (/sup 125/I)BH-CCIK8 reached equilibrium in approximately 150 min. Binding was stable for 4 hr and was reversed by the addition of unlabeled CCK8-sulfated. Dissociation of bound ligand was biphasic and the apparent T/sub 1/2 was 45 min. Analyses of kinetic experiments yielded an association rate constant of 0.58 x 10(8) min/sup -1/ M/sup -1/ and a dissociation rate constant for the slower component of 0.012 min/sup -1/. Dithiothreitol increased and N-ethylmaleimide decreased specific binding of (/sup 125/I)BH-CCK8, indicating that CCK receptor sites involve sulfhydryl groups. In competition experiments, the potency of CCK4 was enhanced 50-fold with addition of protease inhibitors. The rank order of CCK-related peptides was CCK8-sulfated greater than or equal to Gastrin 17 greater than or equal to CCK33 greater than CCK4 greater than or equal to CCK8-desulfated. Proglumide, a proposed CCK antagonist in the periphery and brain, was inactive at 10(-3) M. The specificity of (/sup 125/I)BH-CCK8 binding sites are similar to that reported for (/sup 125/I)BH-CCK33.

• Research Organization: Abbott Labs., North Chicago, IL
• OSTI ID: 5483392
• Journal Information: J. Pharmacol. Exp. Ther.; (United States), Journal Name: J. Pharmacol. Exp. Ther.; (United States) Vol. 232:3; ISSN JPETA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
GUINEA PIGS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANES
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
PEPTIDES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RODENTS
THIOLS
TISSUE DISTRIBUTION
TRACER TECHNIQUES
VERTEBRATES