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抗生素是常用来治疗人类和动物疾病或者促进生长的药品,其以治疗效果显著、抗菌谱广等优点被大量使用[1];据报道,使用的抗生素约90%会进入水体和土壤,不仅污染生态环境,且会对水生动植物、土壤微生物和植物的生存及人类的健康造成较大的威胁[2-4]。研究表明辽河流域地表水中大环内酯类抗生素检测出浓度高达201.88 ng·L−1[5];三峡库区检出的数十种抗生素,林可霉素的浓度高达218 ng·L−1[6];氧氟沙星在美国的医院废水检测中浓度达36 μg·L−1[7];目前世界多地的水源及水厂已检测到抗生素[8],众多的抗生素中,硫酸阿米卡星(amikacin sulfate, AMI)是临床上一种常用的氨基糖苷类抗生素,用于治疗细菌感染的革兰氏阴性的患者,其由于难以降解,在环境中具有生物累积性和持久性,易通过污废水处理厂、陆地生态系统的径流及渗透作用进入水环境[9];研究表明,AMI对蛋白核小球藻的时间依赖毒性较为显著,最大抑制率超过80%[10];此外AMI对人体的肾、耳会造成一定的损伤[11];对环境和人体健康存在风险和危害。
另外,重金属也是环境中典型的污染物之一,常伴随着生活污水、采矿和冶炼等废水进入水环境,微量浓度就可产生较强的毒性作用,对河湖以及地表饮用水产生污染与危害[12];由于重金属具有富集性和不易降解性,且可以通过食物链直接或间接对生物产生累积毒性[13]。铜作为人类最早开采并使用的金属,在历史进程中充当重要的角色,但过量的铜进入生物体内,会引发一系列生物效应,进而产生毒性[14]。
环境中的污染物种类繁多,且以各种形式或浓度混合存在[15],各种污染物的毒性及相互作用不容忽视。此外环境能够影响污染物在其中迁移转化过程的性能,同时影响生活在其中生物的活动行为及代谢方式,所以研究中,污染物所处的环境介质情况越来越受关注[14],成为不可忽视的条件,探究不同环境介质(如pH值)下污染物对生物的毒性作用也成为热门课题。荣宏伟等[16]发现,水体环境的pH值会影响重金属铜对活性污泥的毒性作用;赵娜等[17]发现,pH值会影响Cr6+对小球藻的毒性大小,其表现的毒性为pH值为7时毒性最小,pH值为8时毒性最大;Xu等[18]发现,pH值对个人护理产品的青海弧菌发光抑制率有一定影响。研究表明,pH在化学物质的毒性中具有非常重要的作用,它影响细胞膜对离子的吸收速率和化合物的水解速率[19]。目前有大量的毒性研究是关于重金属和抗生素的,二者的混合物毒性也有一定的报道,但缺少在不同pH值下二者毒性相互作用变化规律的研究,因此,开展不同pH值下重金属和抗生素时间毒性的研究具有重要的实际意义。
该研究拟以硫酸阿米卡星(AMI)和五水硫酸铜(CuSO4·5H2O)为污染物对象,青海弧菌(Vibrio qinghaiensis sp. -Q67, Q67)为受试生物,为确保Q67正常生长[18,20],选用6、7、8、9共4个pH值条件分别进行实验,运用直接均分射线法(direct equipartition ray,EquRay)[21]设计AMI和Cu共5组不同浓度配比的混合物,应用时间毒性微板分析法(Time-dependent microplate toxicity analysis, t-MTA)[22]测定AMI和Cu及其混合物在不同pH值条件、不同暴露时间下的毒性,考虑到浓度加和模型(concentration addition,CA)适用于具有相似毒作用模式/作用机制(mode /mechanism of toxic action,MOA)污染物的混合物毒性评估,而独立作用模型(independent action,IA)适用于具有相异MOA污染物的混合物毒性评估[15,23-25],本研究拟选用IA模型评估在不同暴露时间的AMI和Cu的毒性相互作用,并应用改进的面积浓度比法(the area-concentration ratio method was modified,MACR)[26]评价AMI和Cu之间的毒性相互作用强度,揭示不同pH值条件下AMI和Cu的毒性相互作用变化规律,以期为抗生素与重金属混合物的环境风险评估提供数据和方法参考。
不同pH值对铜和硫酸阿米卡星的青海弧菌时间依赖毒性相互作用的影响
Effects of different pH values on the time-dependent toxic interactions of copper and Amikacin sulfate in Vibrio qinghaiensis sp. -Q67
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摘要: 自然条件下,污染物以各种形式或浓度混合存在,其累积毒性与相互作用对环境健康存在潜在风险,而pH对化学物质的毒性产生非常重要的作用。为了探究不同pH值下污染物的累积毒性与相互作用,该研究以硫酸阿米卡星(Amikacin sulfate, AMI)和五水硫酸铜(CuSO4·5H2O, Cu)为目标污染物,以青海弧菌(Vibrio qinghaiensis sp. -Q67)为受试生物,选用6.0、7.0、8.0、9.0共4个pH值条件分别进行实验,采用直接均分射线法(Direct equipartition ray, EquRay)设计不同浓度配比的代表性混合物,应用时间毒性微板分析法(Time-dependent microplate toxicity analysis, t-MTA)测定其时间-浓度-效应数据,以独立作用(independent action,IA)为参考模型,分析混合物的毒性相互作用,并应用改进的面积浓度比法(the modified area-concentration ratio method,MACR)评价AMI与Cu之间的毒性相互作用强度。结果表明:(1) Cu在不同pH值条件下对Q67的毒性大小顺序为(pH=9)>(pH=7)>(pH=8)>(pH=6),AMI在4个pH值条件下的毒性总体来说相差较小,AMI的毒性高Cu的毒性2—3数量级。(2) Cu和AMI混合物体系毒性具有明显的组分依赖性,混合物体系随AMI组分增加,毒性呈增大趋势,且随着暴露时间的增长,毒性差异更为显著。(3) 不同pH值条件下,pH值为6的混合物体系的pEC50值较小,明显低于pH值为7、8、9混合物体系的pEC50值,pH值为7、8、9的混合物体系之间的毒性值则相差不大。(4) 4个pH值条件下的混合物体系共20条射线,存在协同或加和作用;pH值为6的混合物体系的MACR值低于pH值为7、8、9混合物体系的值,即pH值较低的混合物体系出现的协同作用强度较弱,pH值为7、8、9的混合物体系之间的MACR值则相差不大,毒性相互作用强度较为一致。Abstract: Pollutants are mixed in various forms or concentrations, and their cumulative toxicity and interaction have potential risks to environmental health under the natural condition. While pH plays a very important role in the toxicity of chemical substances. Using Vibrio qinghaiensis sp.-Q67 (Q67) as the test organism, the cumulative toxicity and interction of mixtures of Amikacin sulfate (AMI) and heavy metal Cu were investigated using the time-dependent microplate toxicity analysis method. The experiments were carried out under four pH conditions of 6.0, 7.0, 8.0 and 9.0, respectively. The representative mixtures with different concentrations and ratios were designed by direct equipartition ray (EquRay). The independent action model (IA) was used as reference to analyze the mixture toxicity interactions. The intensity of toxic interaction between AMI and Cu was evaluated using the modified area-concentration ratio method (MACR) .The results showed that: (1) The toxicity order of Cu to photobaterium Q67 at different pH values was: (pH=9)>(pH=7)>(pH=8)>(pH=6). The toxicity difference of AMI to Q67 at four pH values was relatively small, and the toxicity of AMI was 2—3 orders of magnitude higher than that of Cu. (2) The toxicity of Cu and AMI mixture system was obviously component-dependent. The toxicity of the mixture system increased with the addition of AMI components, and the difference of toxicity was more significant with the extension of exposure time. (3) The mixture system at pH 6 showed the highest toxicity and others had the similar toxicity. (4) There were 20 rays in the mixture system at 4 pH values, and synergistic or additive effects existed; The mixture system at pH 6 showed the lowest MACR values and the synergy effects. The mixture system at pH 7, 8 and 9 had the similar MACR values and toxic interaction intensity.
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表 1 实验试剂的基本性质
Table 1. Basic properties of experimental reagents
化合物名称
Chemical Name简称Abbreviation 分子式
Molecular formulaCAS号
CAS No.分子量/(g·mol−1)
Molecular weight纯度/%
Purity储备液浓度/(mol.L−1)
Stock solution硫酸阿米卡星 AMI C22H45N5O17S 149022-22-0 683.68 ≥97.0 2.0×10−5 五水硫酸铜 Cu CuSO4·5H2O 7758-99-8 249.68 ≥99.0 2.0×10−3 表 2 混合物体系各组分浓度配比(pi)
Table 2. Concentration ratio of each component in mixture system (pi)
射线 pH=6 pH=7 pH=8 pH=9 pCu pAMI pCu pAMI pCu pAMI pCu pAMI R1 9.998×10−1 2.200×10−4 9.998×10−1 2.400×10−4 9.998×10−1 2.300×10−4 9.998×10−1 2.300×10−4 R2 9.995×10−1 5.500×10−4 9.994×10−1 5.900×10−4 9.994×10−1 5.700×10−4 9.994×10−1 5.700×10−4 R3 9.989×10−1 1.110×10−3 9.988×10−1 1.180×10−3 9.989×10−1 1.130×10−3 9.989×10−1 1.150×10−3 R4 9.978×10−1 2.210×10−3 9.976×10−1 2.360×10−3 9.977×10−1 2.260×10−3 9.977×10−1 2.290×10−3 R5 9.945×10−1 5.510×10−3 9.941×10−1 5.880×10−3 9.944×10−1 5.630×10−3 9.943×10−1 5.710×10−3 表 3 各射线首次出现协同作用时混合物的浓度
Table 3. The concentration of the mixture when the rays first act synergistically
pH R1 R2 R3 R4 R5 pH=6 — 2.95×10−4 2.21×10−4 8.87×10−5 5.89×10−5 pH=7 — 1.58×10−4 9.31×10−5 2.61×10−5 1.96×10−5 pH=8 4.76×10−4 2.56×10−4 7.68×10−5 4.95×10−5 2.70×10−5 pH=9 — 1.76×10−4 1.07×10−4 4.29×10−5 2.94×10−5 注:“—”表示该条件下没有出现协同作用. Note: “—” indicates that there is no synergistic effect under this condition. -
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