Relationship Between Cytoplasmic Distribution of Mercury and Toxic Effects to Zooplankton and Chum Salmon (Oncorhynchus keta) Exposed to Mercury in a Controlled Ecosystem

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Abstract
Fish and zooplankton were simultaneously exposed to trace, 1, and 5 μg Hg/L. In fish and zooplankton, pathological effects appeared to coincide with saturation of metallothionein and "spillover" of Hg into the high molecular weight protein (enzyme-containing) pool. Coincidental with increases of Hg in tissue were decreases of Cu and Zn. Pathological effects of Hg are explained in terms of tertiary and quaternary structural changes in metalloenzymes resulting from replacement of Cu and Zn by Hg. Decreases in tissue Cu and Zn with increasing Hg concentration are discussed as an intracellular displacement of Cu and Zn by Hg and as duodenal and cellular exclusion processes. Key words: CEPEX, Oncorhynchus keta, zooplankton, mercury, copper, zinc, metallothionein, enzymes, metal tolerance