RT Journal Article SR Electronic T1 A Reevaluation of Neuronal Zinc Measurements: Artifacts Associated with High Intracellular Dye Concentration JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 618 OP 627 DO 10.1124/mol.62.3.618 VO 62 IS 3 A1 Kirk E. Dineley A1 Latha M. Malaiyandi A1 Ian J. Reynolds YR 2002 UL http://molpharm.aspetjournals.org/content/62/3/618.abstract AB The emergence of zinc as a potent neurotoxin has prompted the development of techniques suitable for the measurement of intracellular free zinc ([Zn2+]i) in cultured cells. Accordingly, a new family of Zn2+-sensitive fluorophores has become available. Using ionophore-induced elevations of [Zn2+]i in cultured neurons, we measured [Zn2+]i-induced changes in the novel dyes FuraZin-1 and FluoZin-2 and compared them with the established [Zn2+]i-sensitive fluorophores mag-fura-2 and Newport Green. All of these dyes effectively detected [Zn2+]i, and FuraZin-1, FluoZin-2, and Newport Green showed selectivity for [Zn2+]iover [Ca2+]i and [Mg2+]i. However, the dyes showed little difference in their apparent sensitivity to [Zn2+]i, even though their in vitro affinities for Zn2+ varied from 20 nM to 3 μM. We show herein that this is a consequence of the relatively high concentrations of intracellular dye used in experiments of this nature. Thus, for the measurement of [Zn2+]i, the sensitivity of the reporting system is dominated by the intracellular dye concentration, whereas dye affinity is unimportant. We extend these findings to show that calibration of dye signal to ion concentration is critically dependent on precise measurement of intracellular dye concentration.