Interactions of maitotoxin with voltage-sensitive calcium channels in cultured neuronal cells.
The dinoflagellate toxin maitotoxin (MTX) stimulated 45Ca2+ uptake in cultured NG108-15 neuroblastoma X glioma cells. Depolarizing stimuli (e.g., 50 mM K+) produced an immediate stimulation in Ca2+ uptake, whereas that produced by MTX occurred only after a lag period of about 2 min. MTX did not stimulate Ca2+ uptake into fibroblasts. Both 50 mM K+- and MTX-stimulated Ca2+ uptake was blocked by organic calcium channel antagonists (nitrendipine, D-600, diltiazem) at very low concentrations. Cd2+ was also a potent blocker. The novel dihydropyridine BAY K8644 enhanced Ca2+ uptake in the presence of 50 mM K+ but had no effect in 5 mM Ca2+. However, in the presence of MTX, BAY K8644 stimulated Ca2+ uptake in 5 mM K+. The effects of MTX were not blocked by tetrodotoxin but were decreased in Na+-free medium. MTX did not stimulate Na+ uptake into NG108-15 cells and did not alter [3H]nitrendipine binding to rat brain cortical synaptosomes. It is concluded that MTX may alter the voltage dependence of calcium-channel activation.
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004110:Diltiazem / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005711:Gallopamil / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism*; D008387:Marine Toxins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D009568:Nitrendipine; D035964:Oxocins; D011188:Potassium / Q000494:pharmacology; D000095702:Polyether Toxins
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002104:Cadmium; D002118:Calcium; D004110:Diltiazem; D005711:Gallopamil; D007473:Ion Channels; D008387:Marine Toxins; D009543:Nifedipine; D009568:Nitrendipine; D035964:Oxocins; D011188:Potassium; C020394:maitotoxin; D000095702:Polyether Toxins