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A microscaled mercury saturation assay for metallothionein in fish
Author(s) -
ShawAllen Patricia,
Elliott Muriel,
Jagoe Charles H.
Publication year - 2003
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/02-390
Subject(s) - metallothionein , chemistry , mercury (programming language) , micropterus , environmental chemistry , zinc , bass (fish) , chromatography , biology , fishery , organic chemistry , computer science , programming language
A mercury (Hg) saturation assay for measuring metallothionein (MT) in fish liver was modified by optimizing binding conditions to minimize the mercury and tissue consumed. The revised method uses stable Hg at low concentrations instead of 203 Hg. At the reduced Hg concentrations used, MT concentrations in livers homogenized in saline appeared to increase systematically with dilution in both bluegill sunfish ( Lepomis macrochirus ) and largemouth bass ( Micropterus salmoides ). This error suggested a binding limitation due to sulfhydryl oxidation or competition for and removal of mercury by non‐MT proteins. Homogenizing tissues in trichloroacetic acid (TCA) eliminated the interference. To further evaluate the method, the protocol was tested in the laboratory and field. Metallothionein in bluegill injected with 0.6 mg/kg zinc chloride increased at a rate of 0.03 nmole MT/g liver/ h ( r 2 = 0.53, p = 0.001). Linearity improved when data were corrected for protein content ( r 2 = 0.74, p < 0.0001). Metallothionein levels in bluegill from a coal ash‐contaminated environment were significantly increased over that of hatchery‐reared sunfish ( F = 20.17, p = 0.0003). The microscaled procedure minimizes concerns related to radioisotope use and waste generation while retaining the high sensitivity of the 203 Hg assay.