title: Carbachol-induced accumulation of inositol-1-phosphate in neurohybridoma NCB-20 cells: effects of lithium and phorbol esters.
abstract: Clonal neurohybridoma NCB-20 cells expressed muscarinic cholinergic receptors coupled to phospholipase C. Addition of carbachol in the presence of Li+ to cells prelabeled with 3H-inositol increased 3H-inositol-l-phosphate (3H-IP1) accumulation by more than 4-fold with an EC50 of about 50 microM. This carbachol-induced response was blocked by atropine and pirenzepine with a Ki of 0.5 and 25 nM, respectively. The EC50 of Li+ for the carbachol-induced phosphoinositide turnover was 17 +/- 1.2 mM compared with a value of 1.8 +/- 0.2 mM in brain slices, suggesting the presence of an unusual type of inositol-l-phosphatase in NCB-20 cells. Carbachol-induced IP1 accumulation in these cells was potently and noncompetitively inhibited by the biologically active phorbol esters, phorbol dibutyrate (PDB) and phorbol myristate diacetate (PMA), while the biologically inactive phorbol, 4 beta-phorbol, failed to affect this phosphoinositide breakdown. The basal IP1 accumulation was also significantly attenuated by PDB and PMA but not by 4 beta-phorbol.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001570:Benzodiazepinones / Q000494:pharmacology; D001921:Brain; D002217:Carbachol / Q000494:pharmacology*; D002460:Cell Line; D002712:Chlorides / Q000494:pharmacology*; D006224:Cricetinae; D003412:Cricetulus; D004622:Embryo, Mammalian; D006825:Hybridomas / Q000187:drug effects / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology*; D018021:Lithium Chloride; D051379:Mice; D009447:Neuroblastoma; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology*; D010890:Pirenzepine; D013403:Sugar Phosphates / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D001570:Benzodiazepinones; D002712:Chlorides; D007295:Inositol Phosphates; D010703:Phorbol Esters; D013403:Sugar Phosphates; C002647:inositol 1-phosphate; D015240:Phorbol 12,13-Dibutyrate; D010890:Pirenzepine; D001285:Atropine; D002217:Carbachol; D008094:Lithium; D018021:Lithium Chloride; D013755:Tetradecanoylphorbol Acetate