
%0 Journal Article
%A Lee, J 
%A Treloar, BP 
%A Harris, PM 
%T Metallothionein and trace element metabolism in sheep tissues in response to high and sustained zinc dosages. 1. Characterization and turnover of metallothionein isoforms
%J Australian Journal of Agricultural Research
%D 1994/04/01
%V 45
%N 2
%P 303-320
%K sheep;zinc;copper;metallothionein protein;HPLC
%R https://doi.org/10.1071/AR9940303
%U https://www.publish.csiro.au/paper/AR9940303 
%X Romney wether sheep were given ZnO on a regular basis, as required in protocols for the treatment of facial eczema, at either 12 g ZnO fortnight-1 or 12 g ZnO week-1, and the effect of Zn on the synthesis of different metallothionein (MT) isoforms isolated from liver tissue characterized and quantified. Metallothionein isoforms in liver of dosed and non-dosed sheep were quantitatively determined by reverse phase HPLC, with markedly increased concentrations of total MT-Ia protein found in the liver tissue of Zn-dosed groups (634 pg g-l fresh weight for the weekly dosed group) compared with 49 pg g-1 fresh weight in non-dosed sheep. The concentration of MT-II protein was not significantly increased. Individual sheep varied widely in the relative amounts of each MT isoform expressed with increased amounts of types of MT-Ia especially, and MT-I1 in some animals, which bound predominantly Cu. The half-lives for [35S]-cysteine and 67Zn in MT isoforms from weekly dosed sheep were found to be 2.5-3.5 days and 5-24 h respectively, indicating relatively fast exchange of Zn with MT compared with synthesis. Rate of synthesis for MT-Ia was twice that for MT-11. Data reflecting relationships between MT isoforms, Cu and Zn concentrations in liver are presented and discussed. 
