Ca^(2+)与Pb^(2+)相互作用对斑马鱼胚胎毒性效应的影响

Interaction Between Calcium and Lead Affects the Toxicity to Embryo of Zebrafish (Danio rerio)

为探明Ca2+浓度增加是否会使鱼类早期发育阶段对铅毒性的敏感性升高,以及Ca2+单独减弱铅毒性的浓度范围,选用斑马鱼胚胎作为实验材料,记录在不同的水化学参数条件下,胚胎发育过程中一些具有代表性的毒理学终点,采用相对易于观察且敏感的指标——72 h孵化率进行分析.用Visual MINTEQ2.5.2软件进行溶液中离子的化学形态分析.结果表明,当Ca2+浓度从0.25 mmol/L增加到2.00 mmol/L时,导致了以自由铅离子活度({Pb2+})和溶解态铅总浓度([Pb]T)表示的72 h EC50的增加(表现为发育延迟),两者之间存在良好的线性关系.通过这一线性关系,可以对Ca2+浓度对铅毒性的影响进行预测.这一结果支持了生物配体模型(BLM)概念的假设,说明在胚胎的表面,铅离子与钙离子可能在传输和毒性作用位点上存在竞争作用.而当Ca2+浓度从2.00 mmol/L增加到4.00 mmol/L时,72 h EC50{Pb2+}和72 h EC50[Pb]T并没有显著的增加.

This study tested the hypothesis that increased Ca^2 ＋ content increases the sensitivity of the developing embryos and larvae of zebrafish （ Danio rerio ） to Pb. And the aim of the study was to investigate the extent to which calcium can individually mitigate lead ion toxicity based on the concept of biotic ligand model （BLM）. Embryos of the zebrafish were exposed to various Pb concentrations. Chemical characteristics of water and representative toxicological endpoints of zebrafish embryo were recorded. And general growth retardation as a major toxicological endpoint was used for analysis at 72 h due to its sensitivity and facility. The BLM software of Visual MINTEQ （Version ：2.5.2） was employed to calculate the chemical speciation in the solution. The results showed that when Ca^2＋ concentration increased from 0.25 mmol/L to 2.00 nmol/L, the toxicity of lead on embryos of zebrafish （ Danio rerio） decreased markedly after 72 h. And a large part of these decrease can be explained by the positive linear relations between EC50 {Pb^2＋ }/EC50 [ Pb]T （expressed as lead ion activity/dissolved total concentration） and activity/total concentration of Ca^2＋ , through which the influence of Ca^2＋ on toxicity could be predicted. The results support the assumptions of the BLM and associated with competition between lead and calcium for binding on transport and toxic action sites on biological surfaces. However, when Ca^2＋ concentration increased from 2.00 mmol/L to 4.00 mmol/L, the toxicity of lead on embryos of zebrafish （Danio redo ） seemed to be constant at 72 h.