Degradation of cadmium-thionein in rat liver and kidney.
3H-cystine and 115mCd were incorporated into hepatic and renal cadmium-thionein in response to a subcutaneous administration of 4.4 micronmol of Cd2+ containing 115mCd. Cadmium-thionein bound 115mCd reached a plateau by 24 hrs. and 72 hrs. after the Cd2+ injection in liver and kidney, respectively. The half-life (t 1/2) of 3-H-labeled hepatic cadmium-thionein was 3.5 days, whereas the average t 1/2 of the soluble proteins was 3.7 days. The t 1/2 of the soluble renal proteins was 3.8 days. In marked contrast, the 115mCd content of both hepatic and renal cadmium-thionein was virtually unchanged even 9 days after administration of this radionuclide. These data indicate that the protein moiety of metallothionein is degraded, although there appears to be a concomitant rebinding of Cd2+ to nascent thionein polypeptide chains. Thus the lack of metallothionein degradation, per se, does not account for the long-term retention of Cd2+ in liver and kidney during chronic exposure.
D000818:Animals; D001711:Biotransformation; D002104:Cadmium / Q000378:metabolism*; D006207:Half-Life; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008667:Metalloproteins / Q000378:metabolism*; D008668:Metallothionein / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D013997:Time Factors
D008667:Metalloproteins; D002104:Cadmium; D008668:Metallothionein