| Abstract: |
Total opioid binding in the human neuroblastoma cell line BE(2)-C has a density similar to that found in brain, with a B(max) value of 383 ± 60 fmol/mg protein and a K(D) of 0.4 ± 0.07 nM for the nonselective opioid antagonist 3-I-diprenorphine. Selective assays reveal a binding distribution of mu (38%), delta (16%) and kappa3 (43%) opioid receptors. There is no observable kappa1 or kappa2 binding. The sum of the B(max) values in the selective binding assays (370 ± 39 fmol/mg protein) approximates closely that observed with 3H-diprenorphine, suggesting that mu, delta and kappa3 sites account for most of the binding. The binding selectivities of various opiates and opioid peptides in the BE(2)-C cells are similar to those in rat brain. Delta and mu binding are defined easily by traditional selective ligands. The binding profiles also distinguish clearly mu from kappa3 binding. The selective mu ligand DAMGO competes with mu binding over 35-fold more potently than kappa3 binding, whereas morphine shows a 10-fold selectivity. Functionally, selective mu, delta and kappa3 agonists inhibit forskolin-stimulated cAMP accumulation through distinct receptor mechanisms that are pertussis toxin-sensitive. In addition to demonstrating that BE(2)- C cells provide a useful model system for studying mu, kappa3 and delta receptors, these studies confirm that kappa3 receptors represent a pharmacologically distinct receptor class in this cell line. |
| Keywords: |
controlled study; human cell; animal; cell line; tumor cells, cultured; neuroblastoma cell; recombinant proteins; binding sites; rats; receptor affinity; ligand binding; mu opiate receptor; receptors, opioid, mu; receptor binding; binding competition; enkephalin[2,5 dextro penicillamine]; opioid peptides; delta opiate receptor; receptors, opioid, delta; kappa opiate receptor; enkephalin[2 dextro alanine 4 methylphenylalanine 5 glycine]; human; priority journal; article; receptors, opioid, kappa; support, u.s. gov't, p.h.s.; n methyl n [7 (1 pyrrolidinyl) 1 oxaspiro[4.5]dec 8 yl]benzeneacetamide; bremazocine
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