RT Journal Article SR Electronic T1 Mouse β-TC6 Insulinoma Cells: High Expression of Functional α3β4 Nicotinic Receptors Mediating Membrane Potential, Intracellular Calcium, and Insulin Release JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 899 OP 907 DO 10.1124/mol.105.014902 VO 69 IS 3 A1 Masahiro Ohtani A1 Takami Oka A1 Maryna Badyuk A1 Yingxian Xiao A1 Kenneth J. Kellar A1 John W. Daly YR 2006 UL http://molpharm.aspetjournals.org/content/69/3/899.abstract AB Nicotine elicited membrane depolarization, elevation of intracellular calcium, rubidium efflux, and release of insulin from mouse β-TC6 insulinoma cells. Such responses were blocked by the nicotinic antagonist mecamylamine but not by the muscarinic antagonist atropine. Neither the selective α4β2 antagonist dihydro-β-erythroidine nor the selective α7 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 β-TC6 cells than in rat brain membranes. No binding of 125I-A-85380 was detected, indicating the absence of β2-containing receptors. Reverse transcription-polymerase chain reaction analyses indicated the presence of mRNA for α3 and α4 subunits and β2 and β4 subunits in β-TC6 cells. The binding and functional data suggest that the major nicotinic receptor is composed of α3 and β4 subunits. The β-TC6 cells thus provide a model system for pharmacological study of such nicotinic receptors.