Degradation of cadmium-thionein in rat liver and kidney.
[3 H] Cystine and 115mCd were incorporated into hepatic and renal Cd-thionein in response to sc administration of 4.4 mumol of Cd2+ containing 115mCd. Cd-thionein-bound 115mCd reached a plateau by 24 and 72 h after the Cd2+ injection in liver and kidney, respectively. The half-life (t1/2) of 3 H-labeled hepatic Cd-thionein was 3.5 d, whereas the average t1/2 of the soluble proteins was 3.7 d. The t1/2 of 3 H-labeled renal Cd-thionein was 3.7 d, whereas the average t1/2 of the soluble renal proteins was 3.8 d. In marked contrast, the 115mCd content of both hepatic and renal Cd-thionein was virtually unchanged, even 9 d 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; D002104:Cadmium / Q000378:metabolism*; D003600:Cytosol / Q000032:analysis; D006207:Half-Life; D066298:In Vitro Techniques; 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