title: Synthesis and binding characteristics of the highly selective radiolabelled deltorphin analogues containing 2-aminotetralin-2-carboxylic acid in position 3.
abstract: Following the description of [3H]Ile5,6deltorphin II, when it was reported that changes in hydrophobicity at positions 5 and 6 give rise to analogues with increased delta-receptor affinity and selectivity, new conformationally restricted deltorphin analogues were designed. A synthetic amino acid, 2-aminotetralin-2-carboxylic acid (Atc), was introduced at position 3 instead of Phe in Ile5,6deltorphin I and II, and the resultant compounds were prepared in tritiated form. Opioid binding sites specific for [3H]S-Atc3,Ile5,6deltorphin I and [3H]R-Atc3,Ile5,6deltorphin II were characterized in rat brain membranes. Their binding was saturable, stereoselective and inhibited by delta-selective ligands with high potency. They labelled single class of opioid sites at 35 degrees C with high affinity (Kd approximately 0.3 nM), Bmax values of 130 fmol/mg protein, and very low non-specific binding was observed. Both tritiated deltorphin analogues showed delta-receptor specificity in rat brain, therefore they could represent excellent new radioligands for investigating the complexity of the opioid receptor systems.
authors.affiliation: Institute of Biochemistry, Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Spetea
authors.forename: Z
authors.initials: Z
authors.lastname: Darula
authors.forename: G
authors.initials: G
authors.lastname: Tóth
authors.forename: A
authors.initials: A
authors.lastname: Borsodi
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives* / Q000032:analysis; D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D009842:Oligopeptides / Q000096:biosynthesis / Q000378:metabolism*; D011487:Protein Conformation; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000378:metabolism*; D014316:Tritium
chemical_list: C110305:2-aminotetralin-2-carboxylic acid; D000596:Amino Acids; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D014316:Tritium; C059567:deltorphin; C060208:deltorphin I, Ala(2)-; C060209:deltorphin II, Ala(2)-; D015081:2-Naphthylamine