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Induction of Na + /K + ‐ATPase activity by long‐term stimulation of nicotinic acetylcholine receptors in C2C12 myotubes
Author(s) -
Henning R.H.,
Nelemans S.A.,
Akker J.,
Hertog A.
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb14758.x
Subject(s) - carbachol , nicotinic agonist , acetylcholine receptor , chemistry , muscarinic acetylcholine receptor , endocrinology , muscarinic antagonist , alpha 4 beta 2 nicotinic receptor , myogenesis , medicine , ouabain , stimulation , acetylcholine , biophysics , receptor , myocyte , nicotinic acetylcholine receptor , biochemistry , biology , sodium , organic chemistry
1 To investigate the role of long‐term stimulation of nicotinic acetylcholine receptors (AChRs) on the regulation of membrane potential, non‐contracting C2C12 myotubes were stimulated for 1–4 days with carbachol (10 μ m ) and membrane potentials were measured by the intracellular microelectrode technique after washing out of the drug. 2 The membrane potential (– 45.7 mV) gradually increased by 10.1 mV to − 55.8 mV during 4 days treatment, which was caused by enhanced electrogenic Na + /K + ‐pumping. 3 The concentration‐dependent enhancement of Na + /K + ‐ATPase activity in long‐term carbachol‐treated myotubes (4 days, EC 50 = 5.3 μ m ) was prevented by co‐treatment with the competitive nicotinic AChR antagonist, pancuronium but not by the muscarinic antagonist, atropine. 4 Enhanced Na + /K + ‐ATPase activity still developed in carbachol‐stimulated myotubes during cotreatment (4 days) with the nicotinic AChR‐channel blocker, chlorpromazine (1 μ m ). Membrane depolarization as such, obtained by incubation in high K + medium (40 m m , 4 days) did not enhance Na + /K + ‐ATPase activity. 5 Non‐treated myotubes possessed a high‐affinity ouabain binding site ( K d = 119 n m ) in association with the low Na + /K + ‐pumping activity. Long‐term stimulation of myotubes (4 days) with carbachol or with a combination of carbachol and chlorpromazine was accompanied by the development of an additional low‐affinity ouabain binding site ( K d = 13 μ m ). 6 Binding of monoclonal antibodies directed against either α 1 ‐ or α 2 ‐subunit of Na + /K + ‐ATPase were both increased in myotubes treated with carbachol (4 days). 7 These results support the concept that nicotinic AChRs regulate Na + /K + ‐ATPase activity, independent of the functionality of the receptor‐operated ion‐channel.