title: Maitotoxin stimulates phosphoinositide breakdown in neuroblastoma hybrid NCB-20 cells.
abstract: 1. Maitotoxin (MTX) was an extraordinarily potent stimulant of phosphoinositide breakdown in the neuroblastoma hybrid NCB-20 cells. 2. Maximal responses were obtained at 0.25-0.5 ng MTX/ml, and resulted in increased formation of [3H]inositol mono-, bis-, and trisphosphates. Increased formation of [3H]inositol bis- and trisphosphate was observed as early as 15 sec after the addition of MTX. 3. MTX-induced phosphoinositide breakdown in NCB-20 cells was not antagonized by organic (nifedipine, methoxyverapamil) or inorganic (Mn2+, Co2+, Cd2+) calcium channel blockers. However, the response on phosphoinositide breakdown was completely eliminated in the absence of extracellular calcium. 4. The results suggest that MTX either directly stimulates phosphoinositide breakdown in a calcium-dependent manner or acts indirectly through calcium channels insensitive to organic/inorganic calcium channel blockers.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006224:Cricetinae; D006822:Hybrid Cells / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008387:Marine Toxins / Q000494:pharmacology*; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism; D035964:Oxocins; D010716:Phosphatidylinositols / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism; D000095702:Polyether Toxins
chemical_list: D002118:Calcium; D002121:Calcium Channel Blockers; D007473:Ion Channels; D008387:Marine Toxins; D035964:Oxocins; D010716:Phosphatidylinositols; C020394:maitotoxin; D000095702:Polyether Toxins