Zinc is a nutrient which is essential for good health, including neurological and mental health. The consequences of zinc deficiency range from physical deformities of the central nervous system caused by severe deficiency, to learning and behavioral disorders caused by mild zinc deficiency. This research project will explore the consequences of zinc deficiency on the rate of zinc entry into the brain. Our hypothesis is that the blood-brain barrier, formed by the microvascular endothelium of the brain, possess the ability to actively regulate zinc transport into, and out of, the brain. This enables the brain to sustain relatively adequate zinc nutrition for metabolism during periods of zinc insufficiency. We will test this hypothesis with an in vitro cell culture model of the blood-brain barrier, comprised of porcine capillary endothelial cells growth into a confluent monolayer on permeable membrane which is suspended between two chambers of fluid, representing the capillary lumen and the brain interstitium. This model will enable us to exquisitely manipulate the microvascular cells and their environment in order to probe their transport and metabolism of zinc and their cellular responses to changes in zinc status. Preliminary studies indicate that zinc transport across the blood-brain barrier is a saturable process. This research project will further characterize the mechanism and its regulation. The mechanism of zinc transport will be defined by testing its sensitivity, selectivity, energetics, and kinetics. Susceptibility to physiological perturbations will be explored nd the involvement of other biomolecules or biological messengers will be tested. Armed with an understanding of the transport mechanism, we will then utilize a variety of techniques to define its regulation. The zinc status of the endothelial monolayer will be manipulated in several ways and any subsequent changes in zinc transport will be measured. This will include growing the capillary cells in medium which has been made artificially zinc deficient by chelating or removing the zinc. Additionally, the cells will be grown medium containing serum isolated from zinc deficient pigs. The regulatory mechanisms and signals will be identified. Characterization of the mechanism of zinc transport across the blood-brain barrier and quantification of its regulation will be invaluable in furthering our understanding of zinc transport and neurometabolism. It is also likely to illuminate some of the signals involved in the body's partitioning and distribution of zinc, particularly during periods of nutritional inadequacy. Without these data, it will not be possible to fully comprehend the neurological consequences of zinc deficiency.
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