title: Mouse beta-TC6 insulinoma cells: high expression of functional alpha3beta4 nicotinic receptors mediating membrane potential, intracellular calcium, and insulin release.
abstract: Nicotine elicited membrane depolarization, elevation of intracellular calcium, rubidium efflux, and release of insulin from mouse beta-TC6 insulinoma cells. Such responses were blocked by the nicotinic antagonist mecamylamine but not by the muscarinic antagonist atropine. Neither the selective alpha4beta2 antagonist dihydro-beta-erythroidine nor the selective alpha7 antagonist methyllycaconitine significantly blocked the nicotine-elicited depolarization or the calcium response. The elevation of intracellular calcium did not occur in calcium-free media, indicating that the increase in intracellular calcium was due to the influx of calcium. The rank order of potency for nicotinic agonists was as follows: epibatidine > nicotine = 3-(azetidinylmethoxy)pyridine (A-85380), cytisine, dimethylphenylpiperazinium (DMPP). Cytisine and DMPP seemed to be partial agonists. The density of nicotinic receptors measured by [3H]epibatidine binding was 7-fold higher in membranes from beta-TC6 cells than in rat brain membranes. No binding of 125I-A-85380 was detected, indicating the absence of beta2-containing receptors. Reverse transcription-polymerase chain reaction analyses indicated the presence of mRNA for alpha3 and alpha4 subunits and beta2 and beta4 subunits in beta-TC6 cells. The binding and functional data suggest that the major nicotinic receptor is composed of alpha3 and beta4 subunits. The beta-TC6 cells thus provide a model system for pharmacological study of such nicotinic receptors.
authors.affiliation: Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0820, USA.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ohtani
authors.forename: Takami
authors.initials: T
authors.lastname: Oka
authors.forename: Maryna
authors.initials: M
authors.lastname: Badyuk
authors.forename: Yingxian
authors.initials: Y
authors.lastname: Xiao
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Kellar
authors.forename: John W
authors.initials: JW
authors.lastname: Daly
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001384:Azetidines / Q000494:pharmacology; D001392:Azocines / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000187:drug effects; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D007340:Insulinoma; D008564:Membrane Potentials; D051379:Mice; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011807:Quinolizines / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism*; D000093843:Quinolizidine Alkaloids
chemical_list: D000470:Alkaloids; D001384:Azetidines; D001392:Azocines; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002118:Calcium; D004246:Dimethylphenylpiperazinium Iodide; D007328:Insulin; D009538:Nicotine; D018722:Nicotinic Agonists; D011725:Pyridines; D011807:Quinolizines; D011978:Receptors, Nicotinic; C104288:A 85380; C403530:nicotinic receptor alpha3beta4; C004712:cytisine; D000093843:Quinolizidine Alkaloids; C082748:epibatidine