The effects of zinc deficiency on turnover of cadmium-metallothionein in rat liver.
The object of this experiment was to determine the effects of Zn deficiency on the turnover of Cd-induced metallothionein (MT) in rat liver. Male rats were fed a purified Zn-deficient or Zn-adequate diet. After 13 days, the rats were given three daily injections of Cd2+ totaling 1.5 or 3.0 (Zn-deficient) and 3.0 or 6.0 (Zn-adequate) mg Cd/kg body weight. The MT was labeled by injecting the rats with [35S]cystine 2 hours after the final Cd injection. One, 3 or 5 days after labeling, the rats were killed, and their livers were assayed for MT 35S and metal content. The metal composition of MT (mole %) was 41-42% Cd, 51-54% Zn and 4-7% Cu in the Zn-adequate groups and 64% Cd, 27-31% Zn and 6-9% Cu in the Zn-deficient groups. The half-lives of Cd-induced MT in the Zn-deficient rats were 2.6 days (1.5 mg Cd/kg) and 2.8 days (3.0 mg Cd/kg). In the Zn-adequate rats, the half-lives were 3.6 days (3.0 mg Cd/kg) and 3.1 days (6.0 mg Cd/kg). The half-lives of general, soluble hepatic proteins were 4.1 to 4.3 days in all groups. Despite the stabilizing effect of the higher Cd content, the half-life of hepatic MT in the Zn-deficient rats was significantly shorter than in the Zn-adequate rats. These results indicate that hepatic MT degradation is faster in Zn-deficient animals.
D000818:Animals; D001711:Biotransformation; D002104:Cadmium / Q000032:analysis / Q000378:metabolism*; D003300:Copper / Q000032:analysis; D003553:Cystine / Q000378:metabolism; D006207:Half-Life; D007274:Injections, Intraperitoneal; D008099:Liver / Q000378:metabolism*; D008297:Male; D008668:Metallothionein / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D013462:Sulfur Radioisotopes; D015032:Zinc / Q000032:analysis / Q000172:deficiency*
D013462:Sulfur Radioisotopes; D002104:Cadmium; D003553:Cystine; D003300:Copper; D008668:Metallothionein; D015032:Zinc