Cholinergic responses in cloned human TE671/RD tumour cells |
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Authors: | Francesca Grassi Aldo Giovannelli Sergio Fucile Elisabetta Mattei Fabrizio Eusebi |
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Affiliation: | (1) Dipartimento di Medicina Sperimentale, Universita' di Roma La Sapienza, Rome, Italy;(2) Dipartimento di Medicina Sperimentale, Universita' dell'Aquila, Italy;(3) Laboratorio di Biofisica, Instituto Regina Elena, via delle Messi d'Oro 156, I-00158 Rome, Italy;(4) Istituto Tecnologie Biomediche, CNR, Rome, Italy |
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Abstract: | The cholinergic responses of the human tumour cell line TE671/RD were examined using digital Ca2+ imaging fluorescence microscopy and patch-clamp measurements. In response to stimulation of the muscarinic acetylcholine (ACh) receptor (mAChR), the intracellular concentration of Ca2+ ([Ca2+]i) rose about two-fold, in parallel with inositol 1,4,5-trisphosphate accumulation, measured by chromatographic techniques. By contrast, there was no increment of [Ca2+]i upon stimulation of the nicotinic ACh receptor (nAChR), nor after caffeine application. Electrophysiological experiments showed that TE671/RD cells lack functional voltage-activated Ca2+ channels. The stimulation of the nAChR induced transient whole-cell currents (IACh). Little or no current was detected in isotonic extracellular Ca2+, with Cs+ in the patch pipette. Cell pretreatment with muscarine reduced IACh by about 20%, without consistent modifications of current kinetics. Muscarine applied to the extra-patch membrane under the cell-attached configuration had no obvious effect on ACh-evoked unitary events. In conclusion, in human TE671/ RD cells, muscarinic stimulation increases [Ca2+]i, while nicotinic stimulation does not. In addition, the nAChR exhibits peculiar ion permeability properties and is not functionally regulated by the breakdown of phosphoinositides. |
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Keywords: | Nicotinic acetylcholine receptor Muscarinic acetylcholine receptor TE671/RD cell line Inositol 1,4,5-trisphosphate Phosphoinositide turn-over Ca2+ imaging |
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