Benextramine-neuropeptide Y (NPY) binding site interactions: characterization of 3H-NPY binding site heterogeneity in rat brain.
Pre-incubation of rat brain membranes with 200 microM benextramine followed by extensive dilution and washing to remove unbound ligand reduced Bmax for N-[propionyl-3H]-NPY (3H-NPY) specific binding by 61% relative to control membranes treated identically but in the absence of benextramine. When rat brain membranes were co-incubated with 3H-NPY and 57 microM benextramine, there was a significant shift to the right; the apparent Kd for 3H-NPY binding increased two-fold relative to control membranes. These data are consistent with the hypothesis that benextramine is a competitive and irreversible ligand for a population (60-65%) of rat brain NPY binding sites. 'Paired tube' assays were then used to determine the selectivity of these benextramine-sensitive and insensitive 3H-NPY binding site populations. PYY, NPY and NPY13-36 each displaced 100% of 3H-NPY from rat brain membrane binding sites both in the absence and presence of 1 mM benextramine. In contrast, [Leu31,Pro34]NPY displayed the same binding site selectivity as benextramine in displacing 65% of 3H-NPY from specific binding sites on untreated rat brain membranes, and it failed to displace 3H-NPY from membranes treated with 1 mM benextramine. Thus the selectivity of the benextramine-insensitive 3H-NPY binding site population--PYY > = NPY > NPY13-36 >> [Leu31,Pro34]NPY--is characteristic of a Y2-like NPY binding site population, while the benextramine-sensitive 3H-NPY binding sites appear to be a Y1-like binding site population.
Doughty
M B
MB
Department of Medicinal Chemistry, School of Pharmacy, University of Kansas, Lawrence 66045.
Li
K
K
Hu
L
L
Chu
S S
SS
Tessel
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003538:Cystamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D009478:Neuropeptide Y / Q000031:analogs & derivatives / Q000494:pharmacology; D019894:Peptide YY; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017476:Receptors, Neuropeptide Y / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014316:Tritium
D009478:Neuropeptide Y; D010455:Peptides; D017476:Receptors, Neuropeptide Y; D014316:Tritium; D019894:Peptide YY; C029998:benextramine; D003538:Cystamine