【摘要】 作为主要的重金属污染物,镉(Cd²⁺)和铅(Pb²⁺)对生物体具有不同影响和毒作用机制,然而当它们同时存在于机体内常会表现出不同的联合效应,因此研究以上两种重金属的联合作用极其重要。本研究以模式生物黑腹果蝇（Drosophila melanogaster）为研究对象,采用原子吸收、发育实验、酶学测定以及荧光定量PCR评估Cd²⁺和Pb²⁺以及二者联合对果蝇的影响。向果蝇分别饲喂不同剂量的Cd²⁺(0.05、0.1、0.3、0.5 mmol?L^-1)和Pb²⁺(0.2、0.5、1.5、2.9 mmol?L^-1)以及Cd²⁺+Pb²⁺(0.05+0.2、0.1+0.5、0.3+1.5、0.5+2.9 mmol?L^-1),测定果蝇成虫体内Cd²⁺和Pb²⁺积累量,以及化蛹率、羽化率、抗氧化能力、金属硫蛋白（metallothionein,MTNs）和谷胱甘肽S转移酶（glutathione S-transferase,GST）基因的表达水平。结果表明,果蝇中Cd²⁺和Pb²⁺浓度随着培养基中重金属浓度的上升而增加,当同时加入Cd²⁺和Pb²⁺后,二者积累量进一步增加。单独添加Pb²⁺(0.2、0.5、1.5、2.9 mmol?L^-1)或共同添加Cd²⁺+Pb²⁺(0.1+0.5、0.3+1.5、0.5+2.9 mmol?L^-1)显著降低果蝇化蛹率和羽化率,而Cd²⁺+Pb²⁺联合处理较单独Cd²⁺/Pb²⁺处理表现出更强的效果,且这种效果随着Cd²⁺/Pb²⁺浓度的增加而增强。Cd²⁺+Pb²⁺处理CAT活性较单独Cd²⁺/Pb²⁺处理显著提高。Cd²⁺+Pb²⁺(0.05+0.2、0.1+0.5、0.3+1.5 mmol?L^-1)处理组SOD活性较单独Cd²⁺/Pb²⁺处理,SOD活性无明显变化,但在Cd²⁺+Pb²⁺(0.5+2.9 mmol?L^-1)处理组中SOD活性显著上升;Cd²⁺+Pb²⁺(0.05+0.2 mmol?L^-1)处理组MDA含量较单独Cd²⁺/Pb²⁺处理显著提升,但在处理组Cd²⁺+Pb²⁺(1+0.5、0.3+1.5、0.5+2.9mmol?L^-1)中MDA含量反而较单独的Cd²⁺/Pb²⁺处理有所下降。荧光定量PCR结果表明,在Cd²⁺/Pb²⁺处理下MTNs和Gsts表达水平显著升高。本研究表明重金属联合作用会对生物体产生不同的毒性效应,而MTNs和Gsts两类基因在生物体重金属胁迫下的解毒机制中发挥着至关重要的作用。更多还原

【Abstract】 As the main heavy metal pollutant,Cd²⁺and Pb²⁺have different effect and toxic effects on organisms,however they have a joint effect when they exist simultaneously on organisms.So it is extremely important to study the joint actin of the two heavy metals.In this study,the model organism Drosophila melanogaster was used as the research object,the effects of Cd²⁺,Pb²⁺and their joint action on D.melanogaster were evaluated by atomic absorption,developmental experiments,enzymatic activity determination and real-time quantitative PCR.After feeding D.melanogaster with different doses of Cd²⁺(0.05,0.1,0.3,0.5 mmol?L^-1),Pb²⁺(0.2,0.5,1.5,2.9 mmol?L^-1),and Cd²⁺+Pb²⁺(0.05+0.2,0.1+0.5,0.3+1.5,0.5+2.9 mmol?L^-1),the accumulation of Cd²⁺and Pb²⁺in the body,as well as the pupation rate,emergence rate,anti-oxidative capacity,expression levels of metallothionein（MTNs）and glutathione S-transferase（GST）genes,were measured.The results showed that the concentration of Cd²⁺and Pb²⁺in D.melanogaster increased with the increase of heavy metal concentration in the medium.When Cd²⁺and Pb²⁺were jointly supplemented,the accumulation of Cd²⁺and Pb²⁺further increased.The supplementation of Pb²⁺(0.2,0.5,1.5,2.9 mmol?L^-1)alone and joint supplementation of Cd²⁺+Pb²⁺(0.1+0.5,0.3+1.5,0.5+2.9 mmol?L^-1)significantly reduced the rate of pupation and emergence,also Cd²⁺+Pb²⁺joint treatment had a stronger effect than that of Cd²⁺or Pb²⁺alone.Moreover,the effect also increased with the increase of Cd²⁺/Pb²⁺concentration.The joint supplementation of Cd²⁺and Pb²⁺in each treatment group significantly increased CAT activity compared with Cd²⁺or Pb²⁺treatment alone.In the treatment groups of Cd²⁺+Pb²⁺(0.05+0.2,0.1+0.5,0.3+1.5 mmol?L^-1),the joint supplementation of Cd²⁺and Pb²⁺was compared with Cd²⁺or Pb²⁺alone,and the activity of SOD was not significantly changed,however the activity of SOD significant increased in the treatment group of Cd²⁺+Pb²⁺(0.5+2.9mmol?L^-1).The joint supplementation of Cd²⁺and Pb²⁺significantly increased the MDA content compared with Cd²⁺or Pb²⁺alone in the treatment group of Cd²⁺+Pb²⁺(0.05+0.2 mmol?L^-1),but decreased the MDA content in the treatment groups of Cd²⁺+Pb²⁺(1+0.5,0.3+1.5,0.5+2.9 mmol?L^-1)compared with the Cd²⁺or Pb²⁺treatment alone.The results of real-time quantitative PCR showed that the expression levels of MTNs and Gsts genes were significantly increased after Cd²⁺/Pb²⁺treatment.This study showed that the joint treatment of heavy metals can produce different toxic effects on organisms,while regulation of the expression of the two types of genes,MTNs and Gsts genes,playes a crucial role in the detoxification of organisms under heavy metal stress.更多还原