CELLULAR TARGET SITES OF HEAVY METAL EXPOSED CELLS

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It is the purpose of the proposed research to investigate the degree of heavy metal compartmentalization in test cells and to determine selected specific effects of metal ions on membrane structure and organelle distribution. Studies are to be performed at selected dose levels with conventional transmission electron microscopy to determine if cellular damage has occurred. The organisms Saccharomyces cerevisiae and Chlorella vulgaris will be exposed to various concentrations of five environmentally- significant heavy metals (Cd, Cu, Hg, Pb and Zn) in order to determine EC50 of the cells exposed to the metals. The following will then be determined: (1) the degree of plasma membrane alteration by analyses on the size, shape, number and distribution of elementary particles (proteins) revealed in freeze-fracture preparation, (2) heavy metal location in particular cellular compartments using energy-dispersive X-ray microanalysis of air- dried and/or cryosectioned specimens, (3) cell structures which are most altered by the administration of heavy metal concentrations using morphometric analysis of randomly-oriented thin-sectioned cells, and (4) if any, where heavy metals are localized through the use of atomic absorption spectrophotometry on fraction prepared from disrupted cells. From the results of these studies it is anticipated that we should gain insights as to how heavy metals cause certain detrimental affects on cells. Work to date on Chlorella vulgaris indicates that analysis of membrane particles may be altered by Cd as well as certain other cell organelles and inclusions. This information should be applicable to heavy metal effects at all cellular levels including human effects. It has been found that in most cases cells from any source have a similar response. Thus the cellular data obtained here should be applicable to all cells within certain limits. Use of data from our system should provide data from which models of the cellular response to heavy metals can be obtained. This information can then be used in regard to whole animal response including humans to heavy metals as the damage is, of course, at the cellular level.