Preparation and characterization of a new cholecystokinin receptor probe that can be oxidatively radioiodinated

Journal Article · Sun Jun 01 04:00:00 EDT 1986 · Gastroenterology; (United States)

OSTI ID:5691071

Pearson, R K; Hadac, E M; Miller, L J

Oxidative iodination is the simplest, most efficient, and least expensive method for radiolabeling peptide hormones. It has not been applied to cholecystokinin (CCK), however, because this peptide lacks an unsubstituted tyrosine residue and oxidation abolishes its biologic activity. We report the synthesis, purification, and characterization of the first derivative of CCK that can be radioiodinated with an oxidative method while maintaining full biologic activity and receptor binding affinity. Boc-Tyr-((Thr28, Nle31)CCK-25-33) was synthesized, iodinated using a solid-phase oxidant, and purified on reverse-phase high-pressure liquid chromatography to a specific activity of 2125 Ci/mmol. Both native and iodinated Boc-Tyr-((Thr28, Nle31)CCK-25-33) exhibited efficacy and potency for stimulation of in vitro pancreatic enzyme secretion that were identical to CCK-8. Binding of Boc-/sup 125/I-Tyr-((Thr28, Nle31)CCK-25-33) to rat pancreatic plasma membranes was rapid, reversible, temperature-dependent, saturable, and specific. The abilities of various molecular forms of CCK to compete for this binding paralleled their potencies for stimulation of pancreatic secretion (Kd: CCK-8, 0.8 nM; CCK-33, 3 nM; CCK-8DS, 1 microM; CCK-4, 50 microM), whereas structurally unrelated pancreatic ligands (1 microM) demonstrated no significant competition. These findings suggest that Boc-/sup 125/I-Tyr-((Thr28, Nle31)CCK-25-33) interacts with the same high-affinity pancreatic receptor as the CCK receptor probes previously reported, i.e., the Bolton-Hunter-labeled CCK-33 and CCK-8. This probe also possesses the major advantages of simplicity, efficiency, and cost of the labeling procedure, and the stability and relative oxidation-resistance of the product.

• Research Organization: Mayo Clinic, Rochester, MN
• OSTI ID: 5691071
• Journal Information: Gastroenterology; (United States), Journal Name: Gastroenterology; (United States) Vol. 6; ISSN GASTA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
BODY
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL REACTIONS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
HALOGENATION
INTERMEDIATE MASS NUCLEI
IODINATION
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLING
LIGANDS
LIQUID COLUMN CHROMATOGRAPHY
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PANCREAS
PEPTIDES
PROTEINS
PURIFICATION
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SEPARATION PROCESSES
SYNTHESIS
TRACER TECHNIQUES
VERTEBRATES