Kinetics of binding of cholecystokinin to pancreatic acini

Journal Article · Fri Jul 01 00:00:00 EDT 1988 · American Journal of Physiology; (USA)

OSTI ID:7007816

Wank, S A; Jensen, R T; Gardner, J D ^[1]

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1. National Institutes of Health, Bethesda, MD (USA)

In the present study the authors examined the kinetics of binding of iodinated COOH-terminal octapeptide of cholecystokinin ({sup 125}I-CCK-8) to its receptors on dispersed acini prepared from guinea pig pancreas. At 37{degree}C, binding of {sup 125}I-CCK-8 reached a steady state after 60 min of incubation. Dissociation of bound {sup 125}I-CCK-8 was biphasic, indicating that the labeled peptide binds in two distinct states: a rapidly dissociating state and a slowly dissociating state. Binding of {sup 125}I-CCK-8 in the rapidly dissociating state was maximal within 3 min of incubation, did not depend on incubation temperature or cellular energy metabolism, could be stripped by 0.5 M potassium thiocyanate, and showed accelerated dissociation with CCK-8 or dibutyrylguanosine 3{prime},5{prime}-cyclic monophosphate (Bt{sub 2}cGMP). Binding of {sup 125}I-CCK-8 in the slowly dissociating state was maximal after 60 min of incubation, was decreased by reducing the incubation temperature or inhibiting cellular energy metabolism, was not stripped by 0.5 M potassium thiocyanate, and did not show accelerated dissociation with CCK-8 or Bt{sub 2}cGMP. Computer analysis of the inhibition of {sup 125}I-CCK-8 by CCK-8 under experimental conditions where the rapidly dissociating state predominates demonstrated a complete loss of high-affinity binding sites. The present results demonstrate that labeled CCK-8 can bind in two kinetic states that have not been incorporated into previous models of CCK-receptor interaction based on stoichiometric studies.

• OSTI ID: 7007816
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 255:1; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CHEMICAL REACTIONS
CROSS-LINKING
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
HALOGENATION
INHIBITION
INTERMEDIATE MASS NUCLEI
IODINATION
IODINE 125
IODINE ISOTOPES
ISOTOPES
KINETICS
KININS
MEMBRANE PROTEINS
METABOLISM
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PANCREAS
PEPTIDES
POLYMERIZATION
POLYPEPTIDES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
TEMPERATURE DEPENDENCE
TIME DEPENDENCE