Delta opioid receptors in human neuroblastoma cell lines.

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 delta sites, while only one coexpressed mu sites (SK-N-SH). Together with delta sites previously found in rodent neuroblastoma lines, these results suggest that the expression of delta sites is under less stringent control than that of mu and chi sites. A large number of delta sites (greater than 10,000 sites per cell) is expressed in IMR-32 and NMB neuroblastoma lines. Agonist binding was sensitive to Na+ and guanine nucleotides. The delta sites in IMR-32 and NMB cells were further characterized with delta selective ligands and [3H]DADL tracer. Their delta binding affinities were identical to those of the mu and delta cell line SK-N-SH; therefore the presence of mu sites does not appear to affect the binding behavior of the delta 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, an indication that the delta receptor is highly preserved among different species.