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The influence of dietary and waterborne zinc on heat‐stable metal ligands in rainbow trout, Salmo gairdneri Richardson: quantification by 109 Cd radioassay and evaluation of the assay
Author(s) -
Spry D. J.,
Wood C. M.
Publication year - 1989
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1989.tb03006.x
Subject(s) - metallothionein , rainbow trout , biology , salmo , trout , zinc , size exclusion chromatography , affinity chromatography , binding site , cadmium , cytosol , biochemistry , microbiology and biotechnology , chromatography , chemistry , fish <actinopterygii> , fishery , enzyme , organic chemistry , gene
The 109 Cd binding assay of Eaton & Toal was critically evaluated and then used to assess the induction of cytosolic metal‐binding ligands in rainbow trout exposed to Zn in the diet and/or in the water for 16 weeks. With purified rabbit Cd‐Zn metallothionein (MT), 109 Cd binding and total Cd recovery in the assay were linear up to 5 μg of protein; gel chromatography revealed a single peak. With heat‐denatured extracts of gill, liver and intestine from control and Cd‐ and Zn‐injected trout, 109 Cd binding was generally linear with sample size. Gel chromatography demonstrated that 109 Cd was bound by a protein with the same apparent weight as MT (∼ 11000 daltons), but significant binding occurred also at three other regions [molecular weight (mol wt) >70 000, 30000 and <3000]. In the dietary/waterborne Zn exposure, induced 109 Cd‐binding activity occurred not in the MT peak but in the low mol wt peak (< 3000). Activity in the gill rose in response to both dietary and waterborne Zn, but the liver did not respond. The maximum five‐fold elevation in the gill was primarily a waterborne effect. In the intestine, the maximum rise was 25‐fold due to both factors. The thresholds for induction were > 39 μg Zn | in water, and > 90 mg kg | in the diet, but only when waterborne Zn was also high. There was no correlation between 109 Cd binding and acid soluble thiol levels, which tended to decline at higher Zn exposures.