title: Role of calcium in the regulation of ornithine decarboxylase enzyme activity in mouse colon cancer cells.
abstract: Activity of ornithine decarboxylase (ODC), one of the rate-limiting enzymes in the pathway of polyamine biosynthesis, is regulated by various factors. In this study, we examined the role of Ca2+ in the regulation of ODC enzyme activity in mouse colon cancer cells (MC-26). KCl, a membrane-depolarizing agent that opens the voltage-dependent Ca(2+)-channel to increase intracellular Ca2+, decreased serum-induced ODC enzyme activity in MC-26 cells in a dose-dependent, reversible fashion. Both verapamil and nifedipine, inhibitors of the L-type voltage-dependent Ca(2+)-channel, decreased serum-induced ODC enzyme activity. W-7, a calmodulin inhibitor, decreased ODC enzyme activity in a dose-dependent, reversible fashion while trifluoperazine, another calmodulin inhibitor, failed to affect ODC enzyme activity in MC-26 cells. Our findings indicate that intracellular Ca2+ participates in the regulatory mechanism of ODC enzyme activity in MC-26 cells, although the exact role of Ca2+ is still unclear.
authors.affiliation: Department of Surgery, University of Texas Medical Branch, Galveston 77555.
authors.forename: J
authors.initials: J
authors.lastname: Ishizuka
authors.forename: R J
authors.initials: RJ
authors.lastname: Bold
authors.forename: C M
authors.initials: CM
authors.lastname: Townsend
authors.forename: J C
authors.initials: JC
authors.lastname: Thompson
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology; D017136:Ion Transport; D051379:Mice; D009543:Nifedipine / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D002147:Calmodulin; D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D011189:Potassium Chloride; D014700:Verapamil; D009955:Ornithine Decarboxylase; D009543:Nifedipine; D002118:Calcium