Sensitive and selective detection of zinc ions in neuronal vesicles using PYDPY1, a simple turn-on dipyrrin.

A new class of in vitro Zn(II) chemosensor based on dipyrrin has been developed. 5-(Pyren-1-yl)-4,6-dipyrrin (PYDPY1) was synthesized and exhibited high selectivity and sensitivity to Zn(II) (K(d) of 20 μM) compared to other metal ions. PYDPY1 was applied to the visualization of Zn(II) concentration in hippocampal tissue.

Free zinc ions outside a narrow concentration range are toxic to a variety of cells in vitro.

The zinc(II) ion has recently been implicated in a number of novel functions and pathologies in loci as diverse as the brain, retina, small intestine, prostate, heart, pancreas, and immune system. Zinc ions are a required nutrient but elevated concentrations are known to kill cells in vitro. Paradoxical observations regarding zinc's effects have appeared frequently in the literature, and often their physiological relevance is unclear.

Evidence that the ZNT3 protein controls the total amount of elemental zinc in synaptic vesicles.

The ZNT3 protein decorates the presynaptic vesicles of central neurons harboring vesicular zinc, and deletion of this protein removes staining for zinc. However, it has been unclear whether only histochemically reactive zinc is lacking or if, indeed, total elemental zinc is missing from neurons lacking the Slc30a3 gene, which encodes the ZNT3 protein. The limitations of conventional histochemical procedures have contributed to this enigma.

Synaptic release of zinc from brain slices: factors governing release, imaging, and accurate calculation of concentration.

Cerebrocortical neurons that store and release zinc synaptically are widely recognized as critical in maintenance of cortical excitability and in certain forms of brain injury and disease. Through the last 20 years, this synaptic release has been observed directly or indirectly and reported in more than a score of publications from over a dozen laboratories in eight countries. However, the concentration of zinc released synaptically has not been established with final certainty.

Zinc-secreting Paneth cells studied by ZP fluorescence.

We have used a new family of zinc-specific-responsive fluorescent dyes (ZPs) to study the sequestration and secretion of zinc from Paneth cells, which are located in the bases of the crypts of Lieberkühn within the rat small intestine. Vivid ZP fluorescence zinc staining of Paneth cell secretory granules is seen in both cryostat sections and isolated crypts, providing firm evidence for a pool of labile (rapidly exchangeable) zinc within these cells. We further demonstrate that this ionic zinc pool is secreted under physiological conditions.