title: Activation of muscarinic cholinergic receptors enhances the volume-sensitive efflux of myo-inositol from SH-SY5Y neuroblastoma cells.
abstract: A mechanism used by cells to regulate their volume under hypo-osmotic conditions is the release of organic osmolytes, one of which is myo-inositol. The possibility that activation of phospholipase-C-linked receptors can regulate this process has been examined for SH-SY5Y neuroblastoma cells. Incubation of cells with hypo-osmolar buffers (160-250 mOsm) led to a biphasic release of inositol which persisted for up to 4 h and could be inhibited by inclusion of anion channel blockers - results which indicate the involvement of a volume-sensitive organic anion channel. Inclusion of oxotremorine-M, a muscarinic cholinergic agonist, resulted in a marked increase (80-100%) in inositol efflux under hypo-osmotic, but not isotonic, conditions. This enhanced release, which was observed under all conditions of hypo-osmolarity tested, could be prevented by inclusion of atropine. Incubation of the cells with either the calcium ionophore, ionomycin, or the phorbol ester, phorbol 12-myristate 13-acetate, partially mimicked the stimulatory effect of muscarinic receptor activation when added singly, and fully when added together. The ability of oxotremorine-M to facilitate inositol release was inhibited by removal of extracellular calcium, depletion of intracellular calcium or down-regulation of protein kinase C. These results indicate that activation of muscarinic cholinergic receptors can regulate osmolyte release in this cell line.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism*; D007473:Ion Channels / Q000037:antagonists & inhibitors; D018721:Muscarinic Agonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism*; D009579:Nitrobenzoates / Q000494:pharmacology; D009994:Osmolar Concentration; D010693:Phloretin / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D013654:Taurine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D007473:Ion Channels; D018721:Muscarinic Agonists; D009579:Nitrobenzoates; D011976:Receptors, Muscarinic; D013654:Taurine; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D007294:Inositol; D011494:Protein Kinases; D010738:Type C Phospholipases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010693:Phloretin; D002118:Calcium