Zinc-specific Autometallographic In Vivo Selenium Methods: Tracing of Zinc-enriched (ZEN) Terminals, ZEN Pathways, and Pools of Zinc Ions in a Multitude of Other ZEN Cells

Abstract

S U M M A R YIn vivo-applied sodium selenide or sodium selenite causes the appearance of zinc-selenium nanocrystals in places where free or loosely bound zinc ions are present. These nanocrystals can in turn be silver enhanced by autometallographic (AMG) development. The selenium method was introduced in 1982 as a tool for zinc-ion tracing, e.g., in vesicular compartments such as synaptic vesicles of zinc-enriched (ZEN) terminals in the central nervous system, and for visualization of zinc ions in ZEN secretory vesicles of, e.g., somatotrophic cells in the pituitary, zymogene granules in pancreatic acinar cells, beta-cells of the islets of Langerhans, Paneth cells of the crypts of Lieberkühn, secretory cells of the tubuloacinar glands of prostate, epithelium of parts of ductus epididymidis, and osteoblasts. If sodium selenide/selenite is injected into brain, spinal cord, spinal nerves containing sympathetic axons, or intraperitoneally, retrograde axonal transport of zinc-selenium nanocrystals takes place in ZEN neurons, resulting in accumulation of zinc-selenium nanocrystals in lysosomes of the neuronal somata. The technique is, therefore, also a highly specific tool for tracing ZEN pathways. The present review includes an update of the 1982 paper and presents evidence that only zinc ions are traced with the AMG selenium techniques if the protocols are followed to the letter. T he presence of zinc ions in a subpopulation of synaptic vesicles of a rather numerous group of glutaminergic neurons in the brain and GABAergic, glutaminergic, and possibly glycinergic neurons in the spinal cord and cerebellum, the so-called zinc-enriched (ZEN) neurons, is well established (Slomianka 1992;

Zinc and 4-Hydroxy-2-Nonenal Mediate Lysosomal Membrane Permeabilization Induced by H2O2in Cultured Hippocampal Neurons

“…However, the identity of these zinc-containing vesicles is a controversial issue. Zinc-containing vesicles are detected in Golgi and endoplasmic reticulum in yeast (Devirgiliis et al, 2004;Eide, 2006), lysosomes in astrocytes (Varea et al, 2006), and late endosomes/lysosomes in neuron synaptic vesicles (Danscher and Stoltenberg, 2005;Smith et al, 2007). Interestingly, Sensi et al (2003) showed that mitochondria may function as zinccontaining vesicles, especially on challenge with increased cytosolic zinc levels or oxidative stress.…”

“…It is speculated that zinccontaining vesicles function as a reservoir for zinc to mitigate its potential toxic effect. In astrocytes, zinc-containing vesicles are possibly derived from lysosomes (Varea et al, 2006), whereas zinc-containing vesicles in neurons are stained with markers for endosomes (Danscher and Stoltenberg, 2005;Colvin et al, 2006). However, Sensi et al (2003) demonstrated that mitochondria dynamically take up and release zinc.…”

Glutamate Receptor Ion Channels: Structure, Regulation, and Function

“…Among divalent cations, extracellular Zn 2ϩ most potently inhibits native (Peters et al, 1987;Westbrook and Mayer, 1987) and recombinant NMDA receptors Paoletti et al, 1997;Traynelis et al, 1998). The endogenous ion zinc is packaged into synaptic vesicles in axons terminating in the hippocampus, striatum, amygdala, neocortex, and cortex (Pérez- Clausell and Danscher, 1985;Frederickson, 1989;Valente et al, 2002;Danscher and Stoltenberg, 2005; Paoletti et al, 2009) and may be coreleased with glutamate from the vesicles into the synaptic cleft during neuronal activity. The expression of GluN2A-and GluN2B-containing NMDA receptors may allow zinc to act as an endogenous modulator of the NMDA receptor, depending on its synaptic concentration.…”

Mobile zinc increases rapidly in the retina after optic nerve injury and regulates ganglion cell survival and optic nerve regeneration

“…Most of our studies used autometallography (AMG) (60) to visualize Zn 2+ in the retina because of the selectivity of this method for Zn 2+ per se, its utility for semiquantitative studies, the stability of the reaction product, and high level of reproducibility (61,62). Whereas AMG revealed only modest levels of Zn 2+ in the normal retina, by 6 h after optic nerve crush (NC), the earliest time point we examined using AMG (Methods), the Zn 2+ signal in the inner plexiform layer (IPL) was 4.4 ± 0.3-fold above baseline (mean ± SEM) ( Fig.…”