Induction of cadmium-thionein in isolated rat liver cells

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Abstract
The uptake of Cd by isolated liver cells was linearly related to the Cd concentration to which the cells were exposed in the medium. Cd-treated cells synthesized proteins de novo with the characteristics of Cd-thionein induced in the liver of Cd-treated animals. Thionein from liver cells incorporated Cd and [35S]cysteine, had a Ve/Vo [elution volume/void volume] (Sephadex G-50) of 1.8-1.9, and was separated into 2 subfractions by DEAE-cellulose ion-exchange chromatography. Cycloheximide and actinomycin D when added after a Cd exposure prevented the synthesis of thionein. Addition of actinomycin D after synthesis had started only decreased the total amount of thionein synthesized. The concentration of Cd to which the cells were exposed affected the amount of Cd-thionein synthesized in 6 h. The maximum response occurred when cells were exposed to 0.5 .mu.g of Cd/ml; at higher metal concentrations the total amount of Cd-thionein synthesized declined. This system can be used to study the mode of metal toxicity and the mechanism of Cd-thionein synthesis.