Eaton D L
Toxicol Appl Pharmacol. 1985 Mar 30;78(1):158-62. doi: 10.1016/0041-008x(85)90315-1.
The Cd/hemoglobin affinity assay is finding increasing use as an indicator of metallothionein in a variety of biological tissues. Because the assay relies on the ability of heat-stable proteins to bind Cd, it is important to know the relative affinities of different trace metals to bind to such proteins, relative to Cd. This study examines the ability of 15 trace metals to prevent the binding of Cd to metallothionein using the Cd/hemoglobin affinity assay for metallothionein. Cd, Cu, Hg, and Ag were the only metals tested which significantly inhibited the binding of a fixed concentration (2 microM) of 109Cd to a crude preparation of rat hepatic metallothionein. As, Co, Cr, Fe, Mn, Mo, Ni, Pb, Sn, Th, and Zn had no inhibitory effect at the highest concentrations tested. However, As, Sn, Th, and Zn prevented the precipitation of hemoglobin at relatively low concentrations and, thus, could not be fully tested for inhibitory potency. Cu was the most potent inhibitor, producing more than 90% inhibition at 5 microM, followed by Ag, Hg, and Cd, which produced 76, 72, and 65% inhibition of cadmium binding at 5 microM, respectively. These results suggest that caution should be taken in interpreting metallothionein concentrations obtained by the Cd/hemoglobin affinity assay in tissues which contain relatively a high concentration of Cu, Ag, or Hg, relative to that of Cd.
镉/血红蛋白亲和力测定法在多种生物组织中作为金属硫蛋白的指标正得到越来越广泛的应用。由于该测定法依赖于热稳定蛋白结合镉的能力，了解不同痕量金属相对于镉与此类蛋白结合的相对亲和力很重要。本研究使用镉/血红蛋白亲和力测定法检测金属硫蛋白，考察了15种痕量金属阻止镉与金属硫蛋白结合的能力。镉、铜、汞和银是仅有的经测试能显著抑制固定浓度（2微摩尔）的109镉与大鼠肝脏金属硫蛋白粗制品结合的金属。砷、钴、铬、铁、锰、钼、镍、铅、锡、钍和锌在测试的最高浓度下没有抑制作用。然而，砷、锡、钍和锌在相对较低浓度下可阻止血红蛋白沉淀，因此无法充分测试其抑制效力。铜是最有效的抑制剂，在5微摩尔时产生超过90%的抑制作用，其次是银、汞和镉，它们在5微摩尔时分别对镉结合产生76%、72%和65%的抑制作用。这些结果表明，在解释通过镉/血红蛋白亲和力测定法在相对于镉含有较高浓度铜、银或汞的组织中获得的金属硫蛋白浓度时应谨慎。
