Turnover of metallothioneins in rat liver
| Autor: | I A Bernstein, R D Andersen, W P Winter, J J Maher |
|---|---|
| Rok vydání: | 1978 |
| Předmět: |
inorganic chemicals
Chemical Phenomena Stimulation Biochemistry Metal chemistry.chemical_compound Biosynthesis In vivo Metalloproteins Metallothionein Animals Cysteine Amino Acids Molecular Biology Messenger RNA Chemistry Cell Biology Rats Kinetics Zinc Liver visual_art visual_art.visual_art_medium Electrophoresis Polyacrylamide Gel Female Intracellular Cadmium Half-Life Research Article |
| Zdroj: | The Biochemical journal. 174(1) |
| ISSN: | 0264-6021 |
| Popis: | Two electrophoretically distinguishable metallothioneins were isolated from the livers of Cd2+-treated rats and had thiol group/metal ratios of 3:1, a total metal content, in each of these proteins, of 3.6 atoms of Cd2+ + 2.4 atoms of Zn2+/molecule and 4.2 atoms of Cd2+ + 2.8 atoms of Zn2+/molecule and respective apoprotein mol.wts. of 5844 and 6251. Studies with 1 h pulse labels of [3H]cysteine, given after a single injection of ZnCl2 or CdCl2, showed that these metals stimulated radioactive isotope incorporation into the metallothioneins over the control value by 10- and 15-fold respectively. This stimulation was maximal at 4 h after a single CdCl2 injection and decreased to control values by 16 h, suggesting that either a translational event is responding to free intracellular Cd2+ or a short-lived mRNA is being produced or stabilized in response to the metal treatment. In rats chronically exposed to CdCl2, the metallothioneins increased to 0.2% of the liver wet weight from a control value of 2–4 mumol/kg of liver, with a maximum rate of accumulation of 2–3 mumol/h per kg of liver. The turnover of these proteins in control animals was 0.3–0.6 mumoles/h per kg of liver, measured by the rate of disappearance of 203Hg2+, which binds irreversibly to the metallothioneins. Pretreatment with CdCl2 completely stopped the rapid 203Hg turnover observed in untreated animals. Unlike CdCl2, treatment with ZnCl2 increased the concentration of metallothioneins to a new steady-state pool, 11 mumole/kg of liver, after 10 h. The increase in the zinc-thionein pool by exposure to ZnCl2 in vivo was determined to be primarily due to a stimulation of metallothionein biosynthesis. |
| Databáze: | OpenAIRE |
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