Voltage-sensitive calcium channels in differentiated neuroblastoma X glioma hybrid (NG108-15) cells: characterization by quin 2 fluorescence.
Depolarization of differentiated neuroblastoma X glioma (NG108-15) cells with KCl (50 mM) or veratridine (50 microM) stimulated Ca2+ accumulation, was detected by quin 2 fluorescence. Intracellular Ca2+ concentrations ([Ca2+]i) were elevated about threefold from 159 +/- 7 to 595 +/- 52 nM (n = 12). Ca2+ entry evoked by high extracellular K+ concentration ([K+]o) was voltage-dependent and enhanced by the dihydropyridine agonists, BAY K 8644 and CGP 28 392, in a dose-dependent manner. CGP 28 392 was less potent and less efficacious than BAY K 8644. The (+) and (-) stereoisomers of 202-791 showed agonist and antagonist properties, respectively. (+)-202-791 was less potent, but as efficacious as BAY K 8644. In the absence of KCl, BAY K 8644 had no effect on Ca2+ entry. Voltage-sensitive calcium channel (VSCC) activity was blocked by organic Ca2+ channel antagonists (nanomolar range) both before and after KCl treatment and also by divalent metal cations (micromolar range). High [K+]o-induced Ca2+ accumulation was dependent on external Ca2+, but not on external Na+ ions ([Na]o), and was insensitive to both tetrodotoxin (3 microM) and tetraethylammonium (10 microM). In contrast, veratridine-induced Ca2+ accumulation required [Na+]o, and was blocked by tetrodotoxin, but not by nimodipine (1 microM). Veratridine-induced Ca2+ accumulation was slower (approximately 45 s), smaller in magnitude (approximately 30% of [K+]o-induced Ca2+ entry), and also enhanced by BAY K 8644 (approximately 50%). VSCC were identified in neuronal hybrid (NG108-15 and NCB-20) cells, but not in glial (C6BU-1), renal epithelial (MDCK), and human astrocytoma (1321N1) cells. NG108-15 cells differentiated with 1.0 mM dibutyryl cyclic AMP showed greater VSCC activity than undifferentiated cultures. These results suggest that cultured neural cells provide a useful system to study Ca2+ regulation via ion channels.
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000634:Aminoquinolines; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006224:Cricetinae; D004095:Dihydropyridines / Q000494:pharmacology; D005456:Fluorescent Dyes; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D006822:Hybrid Cells / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D009447:Neuroblastoma / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D000634:Aminoquinolines; D004095:Dihydropyridines; D005456:Fluorescent Dyes; D007473:Ion Channels; D013779:Tetrodotoxin; D003994:Bucladesine; D011189:Potassium Chloride; D014701:Veratridine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D012964:Sodium; C035739:Quin2; D002118:Calcium