Laurin D E, Klasing K C
Department of Avian Sciences, University of California, Davis 95616.
Biochem J. 1990 Jun 1;268(2):459-63. doi: 10.1042/bj2680459.
Metallothionein (MT) is a metal-binding protein rapidly accreted in many tissues in response to trace elements or hormones. To gain an understanding of the regulation of MT accretion, rates of MT synthesis and degradation were determined by using a decay-kinetics technique. A chicken macrophage-cell line (HD11) that rapidly accretes incremental amounts of MT when stimulated with increasing concentrations of Zn2+ or Cd2+ was studied. The maximum rate of MT accretion occurred at 50 microM-Zn2+ or 20 microM-Cd2+. The absolute rate of MT accretion was less in macrophages incubated with 25 microM- as compared with 50 microM-Zn2+, owing to decreased and increased rates of MT synthesis and degradation respectively. The absolute rate of MT accretion was less in macrophages incubated with 10 microM- as compared with 20 microM-Cd2+, owing to a decreased rate of MT synthesis with no change in degradation. Compared with macrophages continually incubated with 50 microM-Zn2+, removal of Zn2+ from medium previously containing 50 microM-Zn2+ decreased the absolute rate of MT accretion, owing to decreased and increased rates of MT synthesis and degradation respectively. Removal of Cd2+ from medium previously containing 20 microM-Cd2+ also decreased the absolute rate of MT accretion in macrophages. Unlike Zn2+ removal, the decrease in MT accretion was due to a decreased rate of MT synthesis with no change in degradation. When macrophages incubated with 50 microM-Zn2+ were subsequently incubated with 20 microM-Cd2+, rates of MT synthesis and accretion were decreased as compared with cells continually incubated with 50 microM-Zn2+ or 20 microM-Cd2+. When macrophages incubated with 20 microM-Cd2+ were subsequently incubated with 50 microM-Zn2+, rates of MT synthesis and accretion were increased as compared with cells continually incubated with 50 microM-Zn2+ or 20 microM-Cd2+. Switching the metal in the incubation medium did not influence the rate of MT degradation. Our results indicate that the rate of MT accretion is determined by variations in the rates of MT synthesis and degradation, depending upon the inducing metal and the concentration of the metal.
金属硫蛋白（MT）是一种金属结合蛋白，在许多组织中，它会因微量元素或激素的作用而快速积累。为了了解MT积累的调控机制，我们采用衰变动力学技术测定了MT的合成和降解速率。我们研究了一种鸡巨噬细胞系（HD11），当用浓度不断增加的Zn2+或Cd2+刺激时，该细胞系会快速积累递增的MT量。MT积累的最大速率出现在50μM - Zn2+或20μM - Cd2+时。与50μM - Zn2+孵育的巨噬细胞相比，与25μM - Zn2+孵育的巨噬细胞中MT积累的绝对速率较低，这分别是由于MT合成速率降低和降解速率增加所致。与20μM - Cd2+孵育的巨噬细胞相比，与10μM - Cd2+孵育的巨噬细胞中MT积累的绝对速率较低，这是由于MT合成速率降低而降解速率未变。与持续用50μM - Zn2+孵育的巨噬细胞相比，从先前含有50μM - Zn2+的培养基中去除Zn2+会降低MT积累的绝对速率，这分别是由于MT合成速率降低和降解速率增加所致。从先前含有20μM - Cd2+的培养基中去除Cd2+也会降低巨噬细胞中MT积累的绝对速率。与去除Zn2+不同，MT积累的降低是由于MT合成速率降低而降解速率未变。当用50μM - Zn2+孵育的巨噬细胞随后用20μM - Cd2+孵育时，与持续用50μM - Zn2+或20μM - Cd2+孵育的细胞相比，MT合成和积累的速率降低。当用20μM - Cd2+孵育的巨噬细胞随后用50μM - Zn2+孵育时，与持续用50μM - Zn2+或20μM - Cd2+孵育的细胞相比，MT合成和积累的速率增加。改变孵育培养基中的金属不会影响MT的降解速率。我们的结果表明，MT积累的速率取决于MT合成和降解速率的变化，这取决于诱导金属及其浓度。
