Characterization of pancreatic somatostatin binding sites with a /sup 125/I-somatostatin 28 analog

Journal Article · Sat Nov 01 04:00:00 EST 1986 · Peptides (Fayetteville, N.Y.); (United States)

DOI:https://doi.org/10.1016/0196-9781(86)90120-8· OSTI ID:6792614

Zeggari, M; Viguerie, N; Susini, C; Esteve, J P; Vaysse, N; Rivier, J; Wunsch, E; Ribet, A

Somatostatin binding to guinea pig pancreatic acinar cell plasma membranes was characterized with an iodinated stable analog of somatostatin 28 (S28): /sup 125/I-(Leu8,DTrp22,Tyr25)S28. The binding was highly dependent on calcium ions. In 0.2 mM free Ca2+ medium, binding at 37 degrees C was saturable, slowly reversible and exhibited a single class of high affinity binding sites (KD = 0.05 +/- 0.01 nM, Bmax = 157 +/- 33 fmol/mg protein). Dissociation of bound radioactivity occurred with biphasic kinetics. Rate of dissociation increased when dissociation was measured at a time before equilibrium binding was reached. In 30 nM free Ca2+ medium, binding affinity and maximal binding capacity were decreased by about 4-fold. Decreasing calcium concentrations increased the amount of rapidly dissociating form of the receptor. Somatostatin 14 antagonist, Des AA1,2(AzaAla4-5,DTrp8, Phe12-13)-somatostatin was active at the membrane level in inhibiting the binding. We conclude that using /sup 125/I-(Leu8,DTrp22,Tyr25)S28 as radioligand allows us to characterize a population of specific somatostatin receptors which are not different from those we previously described with the radioligand /sup 125/I-(Tyr11)-somatostatin. Somatostatin receptors could exist in two interconvertible forms. Calcium ions are an essential component in the regulation of the conformational change of somatostatin receptors.

• Research Organization: Inserm U 151, Toulouse, France
• OSTI ID: 6792614
• Journal Information: Peptides (Fayetteville, N.Y.); (United States), Journal Name: Peptides (Fayetteville, N.Y.); (United States) Vol. 6; ISSN PPTDD
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ALKALINE EARTH METALS
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CALCIUM
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
ENDOCRINE GLANDS
GLANDS
GUINEA PIGS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
METALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PANCREAS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RODENTS
SOMATOSTATIN
TRACER TECHNIQUES
VERTEBRATES