Induction and degradation of copper-induced metallothioneins in rat liver as studied at isometallothionein levels.

Cupric chloride was injected i.p. into female rats in an endeavour to clarify the detailed induction and degradation pathways of hepatic copperbinding protein at isoprotein levels. Injected copper (Cu) in serum decreased to a control level within 6 h, the depletion rate being an intermediate between cadmium (Cd) (within 1 h) and zinc (Zn) (within 1 day). Cu in the liver increased with time after injection and was found mainly in the metallothionein fraction: here it was separated mainly into two isoproteins which corresponded to the two isometallothioneins and were accompainied by Zn. The relative peak height of the two isoproteins changed with time. The overall changes were of an intermediate pattern for those of Cd and Zn loadings.