ISSN:
1095-8649
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
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 (∼ 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 109Cd-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 109Cd binding and acid soluble thiol levels, which tended to decline at higher Zn exposures.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1095-8649.1989.tb03006.x
