The murine IgA-secreting plasmacytoma MOPC-315 expresses somatostatin receptors.
We have previously shown that some neuropeptides had a profound effect on in vitro Ig synthesis (especially IgA) and mitogen-driven murine lymphocyte proliferation. MOPC-315, an IgA-secreting plasmacytoma line, has been extensively used in studies of the regulation of IgA synthesis. In this report we show that the neuropeptide somatostatin (SOM) inhibits proliferation ([3H]thymidine uptake) of MOPC-315 and also inhibits IgA synthesis in vitro. MOPC-315 cells bind both fluorescent SOM and [125I]SOM specifically. On cytofluorimetric analysis, 68 +/- 6.8% (mean +/- SE, n = 7) of MOPC 315 cells labeled with fluorescent SOM and this staining was compatible by incubation with an excess of unlabeled peptide. Specific [125I]SOM binding increased linearly with cell concentration, was rapid and achieved equilibrium after 20 min at 4 degrees C. It was temperature-dependent, readily reversible, and under equilibrium conditions demonstrated a dissociation constant of 1.6 +/- 0.7 nM (mean +/- SE, n = 5). Scatchard analysis showed that MOPC-315 cells had 40,733 +/- 16,050 (mean +/- SE) binding sites for SOM per cell. The characteristics of the interactions of SOM with MOPC-315 cells suggest a specific receptor-mediated mechanism whereby this neuropeptide may modulate lymphocyte function.
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D007070:Immunoglobulin A / Q000096:biosynthesis*; D007457:Iodine Radioisotopes; D007700:Kinetics; D051379:Mice; D010954:Plasmacytoma / Q000032:analysis* / Q000378:metabolism; D017981:Receptors, Neurotransmitter / Q000032:analysis*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000378:metabolism* / Q000494:pharmacology
D007070:Immunoglobulin A; D007457:Iodine Radioisotopes; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013004:Somatostatin; D004247:DNA