title: The role of de novo catecholamine synthesis in mediating methylmercury-induced vesicular dopamine release from rat pheochromocytoma (PC12) cells.
abstract: The purpose of this study was to characterize methylmercury (MeHg)-induced dopamine (DA) release from undifferentiated pheochromocytoma (PC12) cells and to examine the potential role for DA synthesis in this process. MeHg caused a significant increase in DA release that was both concentration- and time-dependent. DA release was significantly increased by 2µM MeHg at 60min and by 5µM MeHg at 30min; 1µM MeHg was without effect. Because DA release induced by 5µM MeHg was associated with a significant percentage of cell death at 60 and 120min, 2µM MeHg was chosen for further characterization of release mechanisms. MeHg-induced DA release was attenuated but not abolished in the absence of extracellular calcium, whereas the vesicular content depleting drug reserpine (50nM) abolished release. Thus, MeHg-induced DA release requires vesicular exocytosis but not extracellular calcium. MeHg also increased intracellular DA and the rate of DA storage utilization, suggesting a role for DA synthesis in MeHg-induced DA release. The tyrosine hydroxylase inhibitor α-methyltyrosine (300µM, 24h) completely abolished MeHg-induced DA release. MeHg significantly increased DA precursor accumulation in cells treated with 3-hydroxybenzylhydrazine (10µM), revealing that MeHg increases tyrosine hydroxylase activity. Overall, these data demonstrate that MeHg facilitates DA synthesis, increases intracellular DA, and augments vesicular exocytosis.
authors: Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA.
authors: Chelsea T
authors: CT
authors: Tiernan
authors: Ethan A
authors: EA
authors: Edwin
authors: John L
authors: JL
authors: Goudreau
authors: William D
authors: WD
authors: Atchison
authors: Keith J
authors: KJ
authors: Lookingland
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D004298:Dopamine / Q000096:biosynthesis* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D005089:Exocytosis / Q000187:drug effects; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism*; D042541:Intracellular Space / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008767:Methylmercury Compounds / Q000633:toxicity*; D016716:PC12 Cells; D051381:Rats; D013997:Time Factors; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D026901:Membrane Transport Proteins; D008767:Methylmercury Compounds; D033921:Vesicular Transport Proteins; C004925:methylmercuric chloride; D002118:Calcium; D004298:Dopamine