LABELING OF NEUROPEPTIDE-Y RECEPTORS IN SK-N-MC CELLS USING THE NOVEL, NONPEPTIDE Y-1 RECEPTOR-SELECTIVE ANTAGONIST [H-3] BIBP3226

The binding of tritium-labelled BIBP3226, nylacetyl)-N-[(4-hydroxy-phe nyl)methyl]-D-arginine amide, to human neuroblastoma SK-N-MC cells was investigated. [H-3]BIBP3226 reversibly binds to neuropeptide Y recept ors of the Y-1 subtype expressed in SK-N-MC cells with a K-D of 2.1+/- 0.3 nM (mean+/-S.E.M., n=3) and a B-max of 58400+/-1100 sites/cell. No n-specific binding did not exceed 30% of the total radioactivity bound at K-D. In competition experiments [H-3]BIBP3226 is concentration-dep endently displaced by neuropeptide Y and its peptide analogues with an affinity pattern neuropeptide Y similar or equal to[Leu(31),Pro(34)]n europeptide Y much greater than neuropeptide Y-(18-36). This rank orde r of potencies is consistent with the interaction of [H-3]BIBP3226 wit h neuropeptide Y receptors of the Y-1 subtype. Therefore, [H-3]BIBP322 6 can be used as selective ligand to study neuropeptide Y Y-1 receptor s.