DEVELOPMENT OF RISK ASSESSMENT METHODS ON HAZARD IDENTIFICATION USING CATALASE MUTANT GENE AS A PREDICTIVE INDEX

本研究旨在建立一种利用过氧化氢酶突变株进行潜在危害的风险评估方法。首先，我们通过将编码来自过氧化氢酶突变小鼠（Cs^B，Cs^c）及其相应野生型（Cs^a）的过氧化氢酶cDNA的质粒转化到过氧化氢酶缺陷型大肠杆菌UM 255中，成功地构建了过氧化氢酶突变型大肠杆菌菌株。过氧化氢酶活性在各缺酶株间存在显著差异。大肠杆菌突变株。Csa的过氧化氢酶活性最高，Cs^c为Cs^a的65.1%，Cs^B为Cs^a的61.7%，UM 255为Cs^a的8.8%。对H_2O_2的敏感性表现出明显的剂量依赖性，与过氧化氢酶活性水平呈负相关。敏感性顺序为UM 255>Cs^B>Cs^c>Cs^a。采用菌落形成率试验和抑菌圈试验对化学品的细胞毒性进行了评价，结果表明，过氧化氢酶缺陷型大肠杆菌的存活率明显低于对照组。大肠杆菌突变体的表达具有显著性 ...更多信息 对苯二酚、邻苯三酚和L-多巴处理后，细胞活力呈剂量依赖性降低，各突变株的细胞活力差异显著，其顺序为Cs^a>Cs^c>Cs^B> UM 255。抑菌圈试验也证实了对苯二酚、连苯三酚和L-多巴的细胞毒性，其中UM 255最敏感，在纸盘周围显示出最大的生长抑制带，其次是Cs^B、Cs^c和Cs^a。过氧化氢酶和抗坏血酸可完全阻断这些化合物的毒性，且呈浓度依赖关系。某些重金属（Hg、Cr、Cd、As、Ni、Fe、Cu）处理也显著降低了这些菌株的存活率，并呈剂量依赖性，表明在氢醌细胞毒性过程中H_2O_2的产生增加，过氧化氢酶在抑制细胞损伤中起保护作用。这些结果支持这些新建立的菌株在风险评估过程中的氧化性化学品的危害识别的有用性。少

This research was aimed at developing a risk assessment method for potential hazards by using catalase mutant strains. At first, we successfully constructed catalase mutant E coli strains by transforming plasmids encoding the catalase cDNA from catalase mutant mice (Cs^b, Cs^c) and its corresponding wild type (Cs^a) into catalase-deficient Escherichia coli UM255. There was a significant difference in catalase activities among each catalase-deficient E. coli mutant. The level of catalase in Csa appeared higher than that in the others, the catalase level in Cs^c was 65.1% of Cs^a, Cs^b was 61.7%, and UM 255 was 8.8% of Cs^a. Susceptibility to H_2O_2 showed a clear dose dependency with negative correlation to catalase activity levels. The susceptibility order was UM255>Cs^b>Cs^c>Cs^a. To assess the cytotoxicity of the chemicals, we employed colony-forming efficiency test and zones of inhibition test, the results demonstrated that survival of catalase-deficient E. coli mutants was signific … More antly reduced by treatment of hydroquinone, pyrogallol and L-Dopa in a dose-dependent manner and the cell viabilities underexposure to these chemicals were also different significantly among each catalase mutant strain, showing the following orders : Cs^a>Cs^c>Cs^b>UM255. The cytotoxicities induced by hydroquinone, pyrogallol and L-Dopa were also confirmed by zone of inhibition test, in which UM255 was the most susceptible, showing the largest zone of growth inhibition surrounding the paper disc, followed by Cs^b, Cs^c and Cs^a. The toxicities of these chemicals were completely blocked by catalase and ascorbic acid in a concentration-dependent relation. Treatment by some heavy metals (Hg, Cr, Cd, As, Ni, Fe, Cu) also significantly reduced the survival of these strains in a dose-dependent manner, suggesting H_2O_2 was increasingly produced in the process of hydroquinone cytotoxicity and catalase played a protective role in inhibiting the cell damage. The results support the usefulness of these newly established strains for hazard identification of oxidative chemicals in a risk assessment process. Less