/sup 125/I-neuropeptide Y and /sup 125/I-peptide YY bind to multiple receptor sites in rat brain

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Mol. Pharmacol.; (United States)

OSTI ID:6569403

Walker, M W; Miller, R J

We describe the preparation of monoiodinated neuropeptide Y (Tyr1-125I-NPY) and monoiodinated peptide YY (Tyr36-125I-PYY). Using these ligands, we detected high, moderate, and low affinity receptor populations in rat brain. Only high and moderate affinity binding sites were suggested by saturation binding studies. Tyr1-125I-NPY bound to 8 +/- 3% of the sites with a Kd of 54 pM (Bmax = 19.4 fmol/mg of protein) and to 92 +/- 3% of the sites with a Kd of 0.92 nM (Bmax = 220.0 fmol/mg of protein). Tyr36-125I-PYY bound to 14 +/- 3% of the sites with a Kd of 23.5 pM (Bmax = 36.4 fmol/mg of protein) and to 86 +/- 3% of the sites with a Kd of 1.9 nM (Bmax = 220.1 fmol/mg of protein). The fragments NPY 13-36 and PYY 13-36 were able to compete with 10 pM Tyr1-125I-NPY for essentially all the binding sites. The fragments were 1 to 2 orders of magnitude less potent than the native peptides. Approximately 50% of the moderate affinity sites, but not the high affinity sites, were reversibly lost in the presence of 5'-guanylyl imidophosphate (Gpp(NH)p), a nonhydrolyzable analog of GTP. Kinetic studies revealed that Tyr1-125I-NPY dissociation could be best described by three dissociation rates. The proportions of slow and intermediate dissociation matched the proportions of moderate and high affinity binding sites, respectively, as suggested by equilibrium studies. There also existed a phase of fast dissociation. When Gpp(NH)p was added during dissociation, the proportion of slow dissociation decreased to the same extent that the fast dissociation was increased. However, the proportion of intermediate dissociation did not change. We propose that rat brain contains a minor population of high affinity NPY binding sites with an intermediate dissociation rate and no sensitivity to Gpp(NH)p.

• Research Organization: Univ. of Chicago, IL (USA)
• OSTI ID: 6569403
• Journal Information: Mol. Pharmacol.; (United States), Journal Name: Mol. Pharmacol.; (United States) Vol. 34:6; ISSN MOPMA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
HYDROLASES
IN VITRO
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HYDROLASES
PEPTIDES
PROTEINS
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SERINE PROTEINASES
TRACER TECHNIQUES
TRYPSIN
VERTEBRATES