Functional aspects of dexamethasone upregulated nicotinic acetylcholine receptors in C2C12 myotubes.
Three days of treatment with the glucocorticoid dexamethasone (1 nM-1 microM) induced a concentration-dependent up-regulation of muscle nicotinic acetylcholine receptor (nAChR) in C2C12 mouse myotubes (EC50 = 10 +/- 7.3 nM), as assessed by [3H]alpha-BuTx binding. The maximum increase in binding amounted 148 +/- 17.6% of control. Parallel electrophysiological measurements employed the patch-clamp technique in cell-attached configuration. The nAChR single channel properties were investigated in the presence of carbachol (1 microM) in the pipette. Treatment with dexamethasone (1 microM, 1-5 days) induced an increase in the number of patches showing channel activity from 30 to 70%. Ion channel characteristics did not differ significantly in control and dexamethasone treated myotubes. Conductance was 32 +/- 3 vs 31 +/- 2 pS, respectively. The time constants of open time events tau 1 and tau 2 were 0.6 +/- 0.1 and 6.6 +/- 1 ms vs 0.6 +/- 0.1 and 6.6 +/- 1 ms, respectively. Closed duration's tau 1 and tau 2 were 1.1 +/- 0.2 and 110 +/- 12 ms vs 1.2 +/- 0.3 and 107 +/- 18 ms. In conclusion, dexamethasone upregulated nAChRs are functional and their electrophysiological parameters are similar to those found in control myotubes.
Maestrone
E
E
Ospedale Civile di Sondrio, Italy.
Lagostena
L
L
Henning
R H
RH
Hertog
A D
AD
Nobile
M
M
D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism; D002460:Cell Line; D003907:Dexamethasone / Q000378:metabolism / Q000494:pharmacology*; D004594:Electrophysiology; D005938:Glucocorticoids / Q000378:metabolism / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects*
D002038:Bungarotoxins; D005938:Glucocorticoids; D007473:Ion Channels; D011978:Receptors, Nicotinic; D003907:Dexamethasone