Panemangalore M, Cherian M G
Chem Biol Interact. 1983 Aug 1;45(3):327-39. doi: 10.1016/0009-2797(83)90079-0.
The interaction of injected zinc and cadmium with metallothionein was investigated in newborn rats. Tissues of 5-day-old rats were removed 24 h after a single injection (Sc) of saline or zinc (20 mg/kg, body wt.) or cadmium (1 mg/kg, body wt.) with 2.5 muCi of 65Zn or 109Cd or 5 muCi of [35S]-cysteine. Injection of zinc resulted in a 75% increase in the hepatic zinc concentration with a concomitant elevation of metallothionein (P less than 0.001), zinc in metallothionein increased by 45% (P less than 0.05); [35S]cysteine incorporation indicated the induced synthesis of metallothionein. Injection of cadmium did not alter either metallothionein or zinc levels in liver, but cadmium in cytosol was preferentially bound to metallothionein. Neither treatment altered hepatic copper metabolism and copper in metallothionein, nor renal zinc and metallothionein levels. These data indicate that zinc injection can elevate hepatic zinc levels and induce metallothionein synthesis in newborn rats despite high basal levels; cadmium injection does not induce metallothionein synthesis, though cadmium is avidly sequestered by pre-existing metallothionein. The differences in the induction of metallothionein by these divalent cations can be explained by the differences in their binding affinities for thiol groups in intracellular metallothionein.
在新生大鼠中研究了注射的锌和镉与金属硫蛋白的相互作用。对5日龄大鼠单次注射生理盐水、锌（20毫克/千克体重）或镉（1毫克/千克体重），同时注射2.5微居里的65Zn或109Cd或5微居里的[35S]-半胱氨酸，24小时后取出组织。注射锌导致肝脏锌浓度增加75%，同时金属硫蛋白水平升高（P小于0.001），金属硫蛋白中的锌增加45%（P小于0.05）；[35S]半胱氨酸掺入表明诱导合成了金属硫蛋白。注射镉未改变肝脏中的金属硫蛋白或锌水平，但细胞溶质中的镉优先与金属硫蛋白结合。两种处理均未改变肝脏铜代谢及金属硫蛋白中的铜，也未改变肾脏锌和金属硫蛋白水平。这些数据表明，尽管基础水平较高，但注射锌可提高新生大鼠肝脏锌水平并诱导金属硫蛋白合成；注射镉虽能被预先存在的金属硫蛋白强烈螯合，但不会诱导金属硫蛋白合成。这些二价阳离子诱导金属硫蛋白的差异可通过它们对细胞内金属硫蛋白中巯基结合亲和力的差异来解释。
