title: Opiate peptide receptors on intact NIE-115 neuroblastoma: radioligand binding properties, intracellular response, and effects of increasing membrane cholesterol.
abstract: Binding of [3H]methionine-enkephalin to intact N1E-115 neuroblastoma cells (competing ligand: naloxone) revealed a homogenous population of receptors with a density (Bmax) of 79.0 +/- 6.5 fmol/mg protein (mean SEM, N = 3) and an apparent Kd of 5.33 +/- 1.63 mM. The order of displacement of [3H]met-enkephalin was met-/leu-enkephalin greater than naloxone greater than morphine, suggesting that it is of the delta receptor class. Specific binding was heat-labile, stereospecific and sensitive to Na+. Adding met-enkephalin to intact neuroblastoma caused reductions of both basal and prostaglandin E1-stimulated levels of cyclic AMP (41.4 +/- 4.0% (N = 6) and 45.1 +/- 2.4% (N = 3) of control levels, respectively). Maximum inhibition (naloxone-reversible) was observed as low as 10(-7) M met-enkephalin. Preliminary results suggest that cells grown in cholesterol-supplemented medium show reduced binding of [3H]met-enkephalin.
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000494:pharmacology; D002999:Clone Cells; D004743:Enkephalin, Leucine / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D008563:Membrane Lipids / Q000502:physiology; D051379:Mice; D009020:Morphine / Q000378:metabolism; D009270:Naloxone / Q000378:metabolism; D009447:Neuroblastoma / Q000032:analysis*; D011957:Receptors, Opioid / Q000032:analysis* / Q000378:metabolism
chemical_list: D008563:Membrane Lipids; D011957:Receptors, Opioid; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D009020:Morphine; D002784:Cholesterol