title: Contaminating levels of zinc found in commonly-used labware and buffers affect glycine receptor currents.
abstract: Zinc is an allosteric modulator of glycine receptor function, enhancing the effects of glycine at nM to low μM concentrations, and inhibiting its effects at higher concentrations. Because of zinc's high potency at the glycine receptor, there exists a possibility that effects attributed solely to exogenously-applied glycine in fact contain an undetected contribution of zinc acting as an allosteric modulator. We found that glycine solutions made up in standard buffers and using deionized distilled water produced effects that could be decreased by the zinc chelator tricine. This phenomenon was observed in three different vials tested and persisted even if vials were extensively washed, suggesting the zinc was probably present in the buffer constituents. In addition, polystyrene, but not glass, pipets bore a contaminant that enhanced glycine receptor function and that could also be antagonized by tricine. Our findings suggest that without checking for this effect using a chelator such as tricine, one cannot assume that responses elicited by glycine applied alone are not necessarily also partially due to some level of allosteric modulation by zinc.
authors.affiliation: Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Garrett L
authors.initials: GL
authors.lastname: Cornelison
authors.affiliation: Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Electronic address: mihic@austin.utexas.edu.
authors.forename: S John
authors.initials: SJ
authors.lastname: Mihic
mesh_terms: D000818:Animals; D002021:Buffers; D004866:Equipment Contamination; D018408:Patch-Clamp Techniques; D018009:Receptors, Glycine / Q000187:drug effects* / Q000502:physiology; D014981:Xenopus; D015032:Zinc / Q000009:adverse effects* / Q000494:pharmacology
chemical_list: D002021:Buffers; D018009:Receptors, Glycine; D015032:Zinc
keywords: Allosteric modulation; EC5; Electrophysiology; GlyR; Glycine receptor; ICP-MS; MBS; N,N,N′,N′-tetrakis(2-pyridylmethyl)ethane-1,2-diamine; TPEN; Tri; Tricine; Xenopus oocytes; Zinc; effective concentration producing 5% of maximal effect; glycine receptor; inductively-coupled plasma mass spectrometer; modified Barth's saline; tricine