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Background and Aims: Recent work has suggested that Zn2+ plays a critical role in regulating acidity within the secretory compartments of isolated gastric glands. Here, we investigate the content, distribution and demand for Zn2+ in gastric mucosa under baseline conditions and its regulation during secretory stimulation. Methods and Findings: Content and distribution of zinc were evaluated in sections of whole gastric mucosa using X-ray fluorescence microscopy. Significant stores of Zn2+ were identified in neural elements of the muscularis, glandular areas enriched in parietal cells, and apical regions of the surface epithelium. In in vivo studies, extraction of the low abundance isotope, 70Zn2+, from the circulation was demonstrated in samples of mucosal tissue 24 hours or 72 hours after infusion (250 mg/kg). In in vitro studies, uptake of 70Zn2+ from media was demonstrated in isolated rabbit gastric glands following exposure to concentrations as low as 10 nM. In additional studies, demand of individual gastric parietal cells for Zn2+ was monitored using the fluorescent zinc reporter, fluozin-3, by measuring increases in free intracellular concentrations of Zn2+ {[Zn2+]i} during exposure to standard extracellular concentrations of Zn2+ (10 mM) for standard intervals of time. Under resting conditions, demand for extracellular Zn2+ increased with exposure to secretagogues (forskolin, carbachol/histamine) and under conditions associated with increased intracellular Ca2+ {[Ca2+]i}. Uptake of Zn2+ was abolished following removal of extracellular Ca2+ or depletion of intracellular Ca2+ stores, suggesting that demand for extracellular Zn2+ increases and depends on influx of extracellular Ca2+. Conclusions: This study is the first to characterize the content and distribution of Zn2+ in an organ of the gastrointestinal tract. Our findings offer the novel interpretation, that Ca2+ integrates basolateral demand for Zn2+ with stimulation of secretion of HCl into the lumen of the gastric gland. Similar connections may be detectable in other secretory cells and tissues. [ABSTRACT FROM AUTHOR]

Down syndrome (DS, trisomy 21) is the most common chromosomal disorder and the leading genetic cause of intellectual disability in humans. In DS, triplication of chromosome 21 invariably includes the APP gene (21q21) encoding the Alzheimer's disease (AD) amyloid precursor protein (APP). Triplication of the APP gene accelerates APP expression leading to cerebral accumulation of APP-derived amyloid-\(\beta\) peptides (A\(\beta\)), early-onset AD neuropathology, and age-dependent cognitive sequelae. The DS phenotype complex also includes distinctive early-onset cerulean cataracts of unknown etiology. Previously, we reported increased A\(\beta\) accumulation, co-localizing amyloid pathology, and disease-linked supranuclear cataracts in the ocular lenses of subjects with AD. Here, we investigate the hypothesis that related AD-linked A\(\beta\) pathology underlies the distinctive lens phenotype associated with DS. Ophthalmological examinations of DS subjects were correlated with phenotypic, histochemical, and biochemical analyses of lenses obtained from DS, AD, and normal control subjects. Evaluation of DS lenses revealed a characteristic pattern of supranuclear opacification accompanied by accelerated supranuclear A\(\beta\) accumulation, co-localizing amyloid pathology, and fiber cell cytoplasmic A\(\beta\) aggregates (\(\sim\)5 to 50 nm) identical to the lens pathology identified in AD. Peptide sequencing, immunoblot analysis, and ELISA confirmed the identity and increased accumulation of A\(\beta\) in DS lenses. Incubation of synthetic A\(\beta\) with human lens protein promoted protein aggregation, amyloid formation, and light scattering that recapitulated the molecular pathology and clinical features observed in DS lenses. These results establish the genetic etiology of the distinctive lens phenotype in DS and identify the molecular origin and pathogenic mechanism by which lens pathology is expressed in this common chromosomal disorder. Moreover, these findings confirm increased A\(\beta\) accumulation as a key pathogenic determinant linking lens and brain pathology in both DS and AD.

Background and Aims: Recent work has suggested that Zn2+ plays a critical role in regulating acidity within the secretory compartments of isolated gastric glands. Here, we investigate the content, distribution and demand for Zn2+ in gastric mucosa under baseline conditions and its regulation during secretory stimulation. Methods and Findings: Content and distribution of zinc were evaluated in sections of whole gastric mucosa using X-ray fluorescence microscopy. Significant stores of Zn2+ were identified in neural elements of the muscularis, glandular areas enriched in parietal cells, and apical regions of the surface epithelium. In in vivo studies, extraction of the low abundance isotope, 70Zn2+, from the circulation was demonstrated in samples of mucosal tissue 24 hours or 72 hours after infusion (250 mg/kg). In in vitro studies, uptake of 70Zn2+ from media was demonstrated in isolated rabbit gastric glands following exposure to concentrations as low as 10 nM. In additional studies, demand of individual gastric parietal cells for Zn2+ was monitored using the fluorescent zinc reporter, fluozin-3, by measuring increases in free intracellular concentrations of Zn2+ {[Zn2+]i} during exposure to standard extracellular concentrations of Zn2+ (10 mM) for standard intervals of time. Under resting conditions, demand for extracellular Zn2+ increased with exposure to secretagogues (forskolin, carbachol/histamine) and under conditions associated with increased intracellular Ca2+ {[Ca2+]i}. Uptake of Zn2+ was abolished following removal of extracellular Ca2+ or depletion of intracellular Ca2+ stores, suggesting that demand for extracellular Zn2+ increases and depends on influx of extracellular Ca2+. Conclusions: This study is the first to characterize the content and distribution of Zn2+ in an organ of the gastrointestinal tract. Our findings offer the novel interpretation, that Ca2+ integrates basolateral demand for Zn2+ with stimulation of secretion of HCl into the lumen of the gastric gland. Similar connections may be detectable in other secretory cells and tissues. [ABSTRACT FROM AUTHOR]