title: Activation of tyrosine hydroxylase by micromolar concentrations of calcium in digitonin-permeabilized adrenal medullary cells.
abstract: In digitonin-permeabilized bovine adrenal medullary cells, Ca2+ (0.1-1.0 microM) caused an activation of tyrosine hydroxylase which was dependent on the presence of ATP. This Ca2+-induced activation of the enzyme was observed even in the presence of optimal concentration of either cyclic AMP or 12-O-tetradecanoylphorbol-13-acetate (TPA) which by itself increased the enzyme activity. Calmodulin inhibitors, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide (W-7), had little effect on the Ca2+-evoked activation of enzyme. These results suggest that micromolar concentrations of Ca2+ activate the activity of tyrosine hydroxylase probably through a Ca2+-dependent phosphorylation in digitonin-permeabilized adrenal medullary cells although the protein kinase(s) responsible for it still remains to be determined.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000313:Adrenal Medulla / Q000201:enzymology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D014446:Tyrosine 3-Monooxygenase; D004072:Digitonin; D002118:Calcium