Intracellular dialysis disrupts Zn2+ dynamics and enables selective detection of Zn2+ influx in brain slice preparations

Authors


Address correspondence and reprint requests to C. W. Shuttleworth, PhD, Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131-0001, USA. E-mail: bshuttleworth@salud.unm.edu

Abstract

We examined the impact of intracellular dialysis on fluorescence detection of neuronal intracellular Zn2+ accumulation. Comparison between two dialysis conditions (standard; 20 min, brief; 2 min) by standard whole-cell clamp revealed a high vulnerability of intracellular Zn2+ buffers to intracellular dialysis. Thus, low concentrations of zinc-pyrithione generated robust responses in neurons with standard dialysis, but signals were smaller in neurons with short dialysis. Release from oxidation-sensitive Zn2+ pools was reduced by standard dialysis, when compared with responses in neurons with brief dialysis. The dialysis effects were partly reversed by inclusion of recombinant metallothionein-3 in the dialysis solution. These findings suggested that extensive dialysis could be exploited for selective detection of transmembrane Zn2+ influx. Different dialysis conditions were then used to probe responses to synaptic stimulation. Under standard dialysis conditions, synaptic stimuli generated significant FluoZin-3 signals in wild-type (WT) preparations, but responses were almost absent in preparations lacking vesicular Zn2+ (ZnT3-KO). In contrast, under brief dialysis conditions, intracellular Zn2+ transients were very similar in WT and ZnT3-KO preparations. This suggests that both intracellular release and transmembrane flux can contribute to intracellular Zn2+ accumulation after synaptic stimulation. These results demonstrate significant confounds and potential use of intracellular dialysis to investigate intracellular Zn2+ accumulation mechanisms.

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