The influence of dietary and waterborne zinc on heat-stable metal ligands in rainbow trout, Salmo gairdneri Richardson: quantification by 109Cd radioassay and evaluation of the assay

D. J. Spry, C. M. Wood

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The 109Cd 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), 109Cd 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, 109Cd binding was generally linear with sample size. Gel chromatography demonstrated that 109Cd was bound by a protein with the same apparent weight as MT (∼11 000 daltons), but significant binding occurred also at three other regions [molecular weight (mol wt) > 70 000, 30 000 and <3000]. In the dietary/waterborne Zn exposure, induced 109Cd-binding activity occurred not in the MT peak but in the low mot wt peak (<3000). Activity in the gill rose in response to both dietary and waterborne Zn, but the liver did not respond. The maximum fivefold 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 l-1 in water, and > 90 mg kg-1 in the diet, but only when waterborne Zn was also high. There was no correlation between 109Cd binding and acid soluble thiol levels, which tended to decline at higher Zn exposures.

Original languageEnglish
Pages (from-to)557-576
Number of pages20
JournalJournal of Fish Biology
Volume35
Issue number4
StatePublished - Oct 1 1989

Keywords

  • diet
  • metal ligands
  • metallothionein
  • rainbow trout
  • zinc

ASJC Scopus subject areas

  • Aquatic Science

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