Calcium influx mediated by nicotinic receptors and voltage sensitive calcium channels in SK-N-SH human neuroblastoma cells.
When SK-N-SH human neuroblastoma cells were exposed to nicotine (NIC) or KCl they showed a dose-dependent transient increase (2- to 4-fold) in intracellular Ca2+ concentration ([Ca2+])i as detected by quin-2 fluorescence, with half maximal effects (EC50) observed at 13 microM and 26 mM, respectively. Tubocurarine and 1-isodihydrohistrionicotoxin potently blocked the NIC-evoked (IC50 congruent to 1 microM and 0.3 microM, respectively), but not the high [K+]o-evoked [Ca2+]i accumulation. The KCl-induced response was inhibited by verapamil and diltiazem (IC50 = 1.4 and 10.9 microM, respectively). Tetrodotoxin (3 microM) and tetraethylammonium (10 microM) had no effect on [Ca2+]i accumulation induced by either agent. Increases in [Ca2+]i could be evoked sequentially by NIC and KCl in the same cells suggesting independent mechanisms of Ca2+ entry. In a Ca2+-free medium, no response to either KCl or NIC was observed. However, when Ca2+ ions were restored, [Ca2+]i accumulation was enhanced to the same extent as cells suspended in a Ca2+-containing buffer. Long-term (18 hr) pretreatment of SK-N-SH cells with pertussis (100 ng/ml) or cholera toxins (10 nM) had no effect on NIC or KCl-induced [Ca2+]i accumulation. Together, these data demonstrate the presence of NIC receptors and voltage-sensitive Ca2+ channels on SK-N-SH neuroblastoma cells, through which [Ca2+]i may be modulated.
Noronha-Blob
L
L
NOVA Pharmaceutical Corporation, Baltimore, Maryland 21224.
Gover
R
R
Baumgold
J
J
D000634:Aminoquinolines; D000664:Amphibian Venoms / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials; D009447:Neuroblastoma; D009538:Nicotine / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*; D014403:Tubocurarine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000634:Aminoquinolines; D000664:Amphibian Venoms; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011978:Receptors, Nicotinic; D009538:Nicotine; C035738:Quin2-acetoxymethyl ester; D002118:Calcium; C007948:histrionicotoxin; D014403:Tubocurarine