title: Characterization of optimized Na+ and Cl- liquid membranes for use with extracellular, self-referencing microelectrodes.
abstract: Self-referencing with ion-selective microelectrodes (ISMs) is a useful approach for monitoring near-real-time ion flux near single cells and across epithelia. While ISMs for H+, Ca2+, and K+ have been optimized for use with self-referencing, ISMs for two other primary inorganic ions, Na+ and Cl-, have not. In this study, we have characterized ISMs based on three Na+ ionophores (I, VI, and X) and one Cl- ionophore to assess their suitability for use with self-referencing. ISMs constructed with Na+ ionophore VI have short response times (approximately 100 ms) but possess nearly an order of magnitude less selectivity for Na+ over K+ than ISMs constructed with Na+ ionophore X. The Na+ ionophore X mixture was enhanced to give it a shorter response time while not compromising its selectivity. A Cl(-)-selective microelectrode was constructed and characterized with superior anionic selectivity compared with previously reported Cl- ISMs used with self-referencing. This Cl(-)-selective microelectrode, however, has a relatively slow response time (approximately 3 s), thus requiring changes to the self-referencing protocol. Self-referencing with these ISMs will enable near-real-time ion flux measurements for Na+ and Cl-.
authors.affiliation: BioCurrents Research Center, Program in Molecular Physiology, Marine Biological Laboratory, Woods Hole, MA 02543, USA. mmesserli@mbl.edu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Messerli
authors.forename: Ira
authors.initials: I
authors.lastname: Kurtz
authors.forename: Peter J S
authors.initials: PJ
authors.lastname: Smith
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008839:Microelectrodes; D012964:Sodium / Q000737:chemistry*; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology
chemical_list: D002712:Chlorides; D007477:Ions; D049993:Sodium Chloride Symporter Inhibitors; D012964:Sodium