title: pH dependence and compartmentalization of zinc transported across plasma membrane of rat cortical neurons.
abstract: In this study, Zn(2+) transport in rat cortical neurons was characterized by successfully combining radioactive tracer experiments with spectrofluorometry and fluorescence microscopy. Cortical neurons showed a time-dependent and saturable transport of (65)Zn(2+) with an apparent affinity of 15-20 microM. (65)Zn(2+) transport was pH dependent and was decreased by extracellular acidification and increased by intracellular acidification. Compartmentalization of newly transported Zn(2+) was assessed with the Zn(2+)-selective fluorescent dye zinquin. Resting cortical neurons showed uniform punctate labeling that was found in cell processes and the soma, suggesting extrasynaptic compartmentalization of Zn(2+). Depletion of intracellular Zn(2+) with the membrane-permeant chelator N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN) resulted in the complete loss of punctate zinquin labeling. After Zn(2+) depletion, punctate zinquin labeling was rapidly restored when cells were placed in 30 microM Zn(2+), pH 7.4. However, rapid restoration of punctate zinquin labeling was not observed when cells were placed in 30 microM Zn(2+), pH 6.0. These data were confirmed in parallel (65)Zn(2+) transport experiments.
authors.affiliation: Program in Neuroscience, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, USA. colvin@ohio.edu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Colvin
mesh_terms: D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D009474:Neurons / Q000378:metabolism*; D011522:Protons; D015363:Quinolones; D051381:Rats; D014105:Tosyl Compounds; D015032:Zinc / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D005029:Ethylenediamines; D005456:Fluorescent Dyes; D011522:Protons; D015363:Quinolones; D014105:Tosyl Compounds; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; C084731:zinquin