title: Intracellular mechanism of Pb(2+)-induced norepinephrine release from bovine chromaffin cells.
abstract: The intracellular mechanism of Pb(2+)-induced release of norepinephrine (NE) was investigated in comparison with Ca2+ in bovine chromaffin cells permeabilized with staphylococcal alpha-toxin. Pb2+ activated NE release at considerably lower concentrations [concentration of free metal giving half maximal metal-dependent release (K0.5) 4.6 nM] than Ca2+ (K0.5 2.4 microM). The release of NE was associated with the release of dopamine-beta-hydroxylase but not lactate dehydrogenase. The maximal secretory responses produced by Pb2+ and Ca2+ were similar and nonadditive. Pb(2+)- and Ca(2+)-dependent releases showed a similar requirement for MgATP and were equally enhanced by protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA) but not by kinase A activator 8-bromoadenosine 3',5'-cyclic monophosphate free base. The protein kinase C inhibitor staurosporine blocked the TPA-stimulated component of secretion but had no effect on the NE release in the absence of TPA. Calmidazolium, an inhibitor of calmodulin, inhibited the secretion evoked by both metals to similar extent. Agents interacting with microtubules (colchicine and vinblastine) or microfilaments (cytochalasin B and phalloidin) had no effect on secretion induced by either metal cation. These observations indicate that both Pb2+ and Ca2+ act at a common site and activate the exocytotic release of NE by an analogous mechanism.
authors.affiliation: Department of Physiology and Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0576.
authors.forename: J L
authors.initials: JL
authors.lastname: Tomsig
authors.forename: J B
authors.initials: JB
authors.lastname: Suszkiw
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000313:Adrenal Medulla / Q000187:drug effects / Q000502:physiology*; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002417:Cattle; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D007854:Lead / Q000633:toxicity*; D009638:Norepinephrine / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D013054:Spectrophotometry, Atomic; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D002147:Calmodulin; D007093:Imidazoles; D015124:8-Bromo Cyclic Adenosine Monophosphate; D007854:Lead; C031938:calmidazolium; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D009638:Norepinephrine