title: Cytosolic acidification and intracellular zinc release in hippocampal neurons.
abstract: In neurons exposed to glutamate, Ca²⁺ influx triggers intracellular Zn²⁺ release via an as yet unclear mechanism. As glutamate induces a Ca²⁺-dependent cytosolic acidification, the present work tested the relationships among intracellular Ca²⁺ concentration ([Ca²⁺](i)), intracellular pH (pH(i) ), and [Zn²⁺](i). Cultured hippocampal neurons were exposed to glutamate and glycine (Glu/Gly), while [Zn²⁺](i), [Ca²⁺](i) and pH(i) were monitored using FluoZin-3, Fura2-FF, and 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein, respectively. Glu/Gly applications decreased pH(i) to 6.1 and induced intracellular Zn²⁺ release in a Ca²⁺-dependent manner, as expected. The pH(i) drop reduced the affinity of FluoZin-3 and Fura-2-FF for Zn²⁺. The rate of Glu/Gly-induced [Zn²⁺](i) increase was not correlated with the rate of [Ca²⁺](i) increase. Instead, the extent of [Zn²⁺](i) elevations corresponded well to the rate of pH(i) drop. Namely, [Zn²⁺](i) increased more in more highly acidified neurons. Inhibiting the mechanisms responsible for the Ca²⁺-dependent pH(i) drop (plasmalemmal Ca²⁺ pump and mitochondria) counteracted the Glu/Gly-induced intracellular Zn²⁺ release. Alkaline pH (8.5) suppressed Glu/Gly-induced intracellular Zn²⁺ release whereas acidic pH (6.0) enhanced it. A pH(i) drop to 6.0 (without any Ca²⁺ influx or glutamate receptor activation) led to intracellular Zn²⁺ release; the released Zn²⁺ (free Zn²⁺ plus Zn²⁺) bound to Fura-2FF and FluoZin-3) reached 1 μM.
authors.affiliation: Departments of Psychiatry and Pharmacology, The Psychiatric Institute, The University of Illinois at Chicago, Chicago, Illinois 60612, USA. lkiedr@psych.uic.edu
authors.forename: Lech
authors.initials: L
authors.lastname: Kiedrowski
mesh_terms: D000465:Algorithms; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003470:Culture Media; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism*; D005452:Fluoresceins / Q000494:pharmacology; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D003470:Culture Media; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D018698:Glutamic Acid; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D015032:Zinc; D002118:Calcium