Cellular Mechanism of Heavy Metal Detoxification in CrustaceansEPA Grant Number: R823068
Title: Cellular Mechanism of Heavy Metal Detoxification in Crustaceans
Investigators: Ahearn, Gregory A.
Institution: University of Hawaii at Honolulu
EPA Project Officer: Hiscock, Michael
Project Period: August 1, 1995 through August 1, 1998
Project Amount: $462,981
RFA: Exploratory Research - Minority Institutions (1995) Recipients Lists
Research Category: Water , Land and Waste Management , Ecosystems , Air , Aquatic Ecosystems
Description:This study is a three-part effort to investigate the cellular mechanisms by which freshwater (Macrobrachium rosenbergii) and marine (Homarus americanus) crustaceans sequester and detoxify environmental heavy metals. Zinc will be chosen as an example of an "essential" metal (i.e., one needed for life) and cadmium as an example of a "non-essential" metal (one with no biological function). First, the effects of these metals at different environmental concentrations on the survival and growth rates of larvae of the two animals will be investigated. Second, animals from these toxicity experiments will be fixed and their tissues thin-sectioned for electron microscopic x-ray microprobe elemental analyses to anatomically localize and quantify the concentrations of each metal. This approach will provide a temporal pattern of metal sequestration within appropriate tissues and will localize the cellular compartments responsible for the sequestration events. Third, isolated membrane vesicles will be prepared from gastrointestinal epithelial cellular endosomes and lysosomes which are believed to be the intracellular compartments responsible for storing metals during detoxification. These purified membrane vesicles will be used in isotopic flux experiments to physiologically characterize the transport mechanisms for movements of 65Zn and 109Cd from epithelial cytosol to cytosome contents. In addition, because metal sequestration events include the complexation of cationic metals with sulfate and phosphate, the transmembrane transport processes responsible for moving these anions from cytosol to cytosome contents will also be investigated using 35SO4 and 32PO4.
These combined studies should show, for the first time, the cellular mechanisms of freshwater and marine crustaceans that are capable of accumulating and detoxifying "essential" and "non-essential" heavy metals. Once the steps involved in these detoxification processes are understood, specific means might be developed to reverse them during a temporary purging interval in unpolluted waters so that the animals can be made suitable for human consumption.