Corami F, Capodaglio G, Turetta C, Bragadin M, Calace N, Petronio B M
Dipartimento di Scienze Ambientali, Università Ca' Foscari, Venezia.
Ann Chim. 2007 Jan-Feb;97(1-2):25-37. doi: 10.1002/adic.200690083.
The effects of humic acids and fulvic acids isolated from the River Arno (Italy) on the bioavailability and toxicity of cadmium and copper were assessed in relation to changes in their speciation. Measurements of the complexing capacity of solutions containing these organic ligands were carried out by a titration procedure followed by DPASV and toxicity tests were carried out using lysosomes isolated from rat liver. The complexing capacity of the physiological medium containing about 13 mg/L of humic acids, expressed as ligand concentrations, was 0.30 and 0.072 micromol/L for cadmium and copper respectively; the corresponding conditional stability constants were 4.2 x 10(11) and 1.3 x 10(8) (mol/L)-1. The complexing capacities of the solution containing the same amount of fulvic acids were 0.33 and 0.164 micromol/L for cadmium and copper respectively, the conditional stability constants were 3.2 x 10(11) and 2.4 x 10(7) (mol/L)-1. The humic acids reduced the toxicity of cadmium by about 5 times: the EC50 changed from 4.4 to 20.4 micromol/L. The dose effect curve of copper presented a bi-sigmoid trend and two EC50 values can be determined: The EC50(1) in the presence of humic acids changed from 2.0 to 3.1 micromol/L, while the EC50(2) increased from 22.3 to 45.3 micromol/L. The fulvic acids reduced the cadmium toxicity by about the same amount as humic acids, from 4.4 to 18.6 micromol/L, but they had no effect on copper toxicity. Analysing the chemical speciation of cadmium and copper in the presence of humic components and under toxicity test conditions we can say that the appreciable decrease of EC50 is not related to changes in their speciation; we can hypothesize that this is due to different processes, as well as to blocking of the lysosomal membrane. On the basis of the shape of the dose-effect curves obtained for cadmium and copper respectively, we can say that the toxic effects of the two metals are different and we can hypothesize that copper could exercise its toxic activity by inhibiting the ATP-driven proton pump and the function of the Cl- selective channel.
评估了从意大利阿尔诺河分离出的腐殖酸和富里酸对镉和铜生物有效性及毒性的影响，并研究了其形态变化。通过滴定法结合微分脉冲阳极溶出伏安法（DPASV）测定了含有这些有机配体的溶液的络合能力，并使用从大鼠肝脏分离的溶酶体进行了毒性测试。含有约13mg/L腐殖酸的生理介质的络合能力，以配体浓度表示，镉为0.30μmol/L，铜为0.072μmol/L；相应的条件稳定常数分别为4.2×10¹¹和1.3×10⁸（mol/L）⁻¹。含有相同量富里酸的溶液的络合能力，镉为0.33μmol/L，铜为0.164μmol/L，条件稳定常数分别为3.2×10¹¹和2.4×10⁷（mol/L）⁻¹。腐殖酸使镉的毒性降低了约5倍：半数有效浓度（EC50）从4.4变为20.4μmol/L。铜的剂量效应曲线呈双S形趋势，可确定两个EC50值：存在腐殖酸时的EC50(1)从2.0变为3.1μmol/L，而EC50(2)从22.3增加到45.3μmol/L。富里酸使镉的毒性降低程度与腐殖酸大致相同，从4.4降至18.6μmol/L，但对铜的毒性没有影响。分析在腐殖成分存在下以及毒性测试条件下镉和铜的化学形态，我们可以说EC50的显著降低与它们的形态变化无关；我们可以推测这是由于不同的过程以及溶酶体膜的阻断。根据分别获得的镉和铜的剂量效应曲线形状，我们可以说这两种金属的毒性作用不同，并且我们可以推测铜可能通过抑制ATP驱动的质子泵和Cl⁻选择性通道的功能来发挥其毒性作用。
