Mercury is a pervasive occupational and environmental neurotoxicant of unknown cellular mechanism. A preliminary study by the P.I. showed that mercury in low concentration selectively inhibits glutamate uptake into primary cell cultures of mouse cerebral astrocytes. Glutamate and related endogenous neuroexcitants are themselves suspected of involvement in adult-onset primary neurodegenerative disorders. It is hypothesized that selective blockade of glutamate inactivation may be a contributory mechanism in mercury neurotoxicity. The proposed research will determine whether a cellular basis exists for this hypothesis.
The aim of the research is to explore the selective impairment of characterized amino acid transport systems by the toxic action of mercuric chloride and methylmercury(II) chloride. Anionic (Systems X-AG, X-A), neutral (Systems A, L, ASC, N, beta, GABA), and cationic (System y+) amino acid transport systems will be probed. This analysis will be correlated with cell mercury content and subcellular distribution, and with functional and morphologic status in mouse cerebral astrocytes. Radioactive tracers will be used to measure amino acid transport, leucine incorporation into protein, glucose utilization and mercury content of the astrocytes. Membrane integrity will be probed by vital dye exclusion and tracer efflux. Ultrastructural analysis of the cells and scanning X-ray microanalysis of mercury distribution will be carried out using quick-freeze fixation and cryopreparative techniques. A consultative and collaborative arrangement has been made for fluorometric assay of intermediates and metabolites of glycolytic and oxidative pathways. The proposed research will provide answers to fundamental questions concerning the cellular neurotoxic mechanism of mercury. These answers will be in a form that can be quantitatively, and therefore meaningfully, related to in vivo studies. The results will have a direct bearing upon (a) the need to provide a sound basis for defining tolerable tissue burdens of mercury in humans, (b) alternative therapeutic approaches in management of mercury intoxication, and (c) exploration of possible linkages between environmental neurotoxicants and primary neurodegenerative disorders.
Showing the most recent 10 out of 17 publications
