Delta opioid receptor in human neuroblastoma cell lines

Abstract

Opioid receptor sites were detectable in 4 out of 9 human neuroblastoma cell lines tested, in the human retinoblastoma line Y79 NHT C10 and in the mouse neuroblastoma line Neuro 2A. All of these cell lines expressed δ sites, while only one coexpressed μ sites (SK-N-SH). Together with δ sites previously found in rodent neuroblastoma lines, these results suggest that the expression of δ sites is under less stringent control than that of μ and χ sites. A large number of δ sites (> 10,000 sites per cell) is expressed in IMR-32 and NMB neuroblastoma lines. Agonist binding was sensitive to Na + and guanine nucleotides. The δ sites in IMR-32 and NMB cells were further characterized with δ selective ligands and [ 3H]DADL tracer. Their δ binding affinities were identical to those of the μ and δ cell line SK-N-SH; therefore the presence of μ sites does not appear to affect the binding behavior of the δ sites by any potential interaction among the binding proteins. Further, close correlations were found when comparing ligand binding in the human neuroblastoma cell lines with those of mouse neuroblastoma cells and rodent brain, and indication that the δ receptor is highly preserved among different species.